The Westchester will offer more of a range of price points than Greenwich Ave, if Theory does not work out.
I love the fit of Theory and their clothes wear well. I like more tailored clothes and although I love that artsy look of flowing fabric, it overpowers me at barely 5’1.
I had never bought anything from Theory. I just looked at their website and I know why! I’ve never spent $300 for pants before but they look gorgeous and well made. I’ve spent a lot for dresses and coats, but never pants. (probably at the most $150 for pants) I noticed the sizes are S, M, L How do they run? True to size? In pants I’d probably be a large and on top, a medium, unless they tend to run larger or smaller.
mathmom: this may be a good time to invest in a really nice pair of pants to wear with many different tops as eb suggested.
Theory sizes their clothes starting at 0. I think Theory runs small. I’m 5"1 approx 110–115 depending on the season. I wear a zero in most of their pants but have bought in size 2. The dress I bought last spring is a 4.
I have Theory pants in my closet that are at least 5 years old. They are made very well and also really hold up fashion wise, too. But I always buy at least one new pair a year and retire the oldest.
I am like Harvestmoon, I can’t wear flowy clothes.
I’ve never spent more than whatever NYD jeans cost and thought that was a lot! But it’s not like black pants go out of style.
I have one or two slightly flowy things in my closet, but it’s really not my style. It will be something like a broomstick skirt (very useful in the middle east) or wide pants. One or two things you put over other shirts that other people have given me.
Imo, for a really nice black pant the price is worth it. i am sure you will find a pair that fits you perfectly and you will wear them all the time. It’s like having the perfect LBD - you know it will always be right for almost every occasion.
I bought nice black and navy pants at BR, in petite. Saves money from having them shortened. Mathmom doesn’t need to worry about hemming, but some BR pants fit well, and are less expensive than theory.
I am comfortable in nice pants, and splurge on Elle tahari silk blouses or sweaters. That is my GO look for fancy restaurants, holiday parties.
I still would suggest that mathmom go to a clothing store and be helped by a salesperson. Not necessarily Theory…but someone who can help put an outfit together that you may not have thought of before! I’m getting mixed messages: mathmom: you usually wear more structured clothing? It sounded as if you wore many flowy, artsy pieces. If you usually wear more structured, then you’ll be fine for this event, imo. Have fun shopping! 
Earlier in this thread, some posters recommended Ponte material. I think that’s a wonderful choice. These here are less than the $300 that Theory wants but still very fashionable.
^^These are even cheaper, mathmom and are the NYDJ that you are already familiar with.
I could get those last three in three different colors too! Theory and Nordstrom are in the same mall I think.
I’d say my style to the extent I have any is structured - really I wear jeans and a plain t-shirt most days, and dress it up with a blazer or jacket. I’ve got a lot of sweaters because in the winter I am always cold. I wear capris in the summer. I really like a man’s white button up shirt with jeans.
@chocchip I like both those Ponte trousers. I really prefer the slim leg trouser on just about everyone. Much more youthful. I cannot wear Ralph Lauren pants because of the boxy fit and they are mostly high waisted as well. I feel like a frump when I try those pants on.
The nice thing about ponte pants is that they are washable. I wash a lot of “dryclean only” stuff, but Theory trousers and jackets are not on that laundry list. 
I prefer slim leg too. Also, @mathmom mentioned (I think) that she is not that keen on much of a heel. I think those black pants with a flair on the bottom would only look good with some heel. So, if she is going to opt for a very low heel, a slim leg pant might be a better option.
I like slimmer pants in general. I ended up tossing most of my LL Bean pants because I felt so fumpyin them.
Always interesting to see what people wear. I’m with Abasket (I think that was who posted) and would wear a deconstructed probably solid color above the knee dress, tights and boots and accessorize with a scarf or wrist and neck jewelry or both just depending on the mood. I almost never find fall-winter pants that don’t look severe and office-like so I love clicking the links to see what people would wear. I do have a pair of heavy linen black pants that are not fitted that work well with the Sundance top and more boho-ish tops for events like this in warmer weather.
I agree - get some lovely black pants. You will have good future use of them too. It is a worthwhile investment if you wear them a lot. (For me the challenge is that most nicer pants are dry clean only, and I try stick with machine washable wardrobe.)
Clothes I have to dryclean is one of the things I despise, though I’ve been known to buy them anyway. I’ve also been known to just wash them as delicates to see what happened. (They survived.)
So reporting back…
I did get myself off to Nordstroms where I bought BunsenBurner’s suggestion for nicer NYDJ black pants. While I was there I also got some grey pants and and a very dark olive pair of legging/pants/skinny jeans. They were indeed very helpful and maybe I should have had them find me tops to, but pants was all I could handle for one trip, especially since I have been battling some stupid respiratory crud for the last two weeks. I figured there had to be something in my closet. I thought I’d wear the red pagoda shirt from soft surroundings, but it seemed too low cut for lunch so since it was going to be in the 70s I went with a nice short sleeved crisp blouse that I always look good in (It’s got those darts so it has some shape.) I wavered between a German boiled wool jacket and an LL Bean tweed hunting jacket, but the LL Bean one is a better length with the shirt and goes with the booties. Which even with my recovering broken toe are remarkably comfortable for a shoe with a good 1"+ heel. I wore a pretty low key necklace and a pair of origami earrings my son had, and an arty pin on the lapel of the blazer.
I’d say I was dress about right, I always look around and everyone just looks wealthier than me. (Which they probably are mostly!) The host was downright dowdy in black courderoys, a plain blouse and a quilted jacket. Gray hair in a page boy pulled back with pins just one step up from bobby pins. Very nice woman.) The headmistress wore a skirt suit. Some women wore shift dresses with expensive looking blazers. Red was popular and so was black. One woman had on a black leather skirt, black jacket and black blouse. Most women though wore gray or black pants, a nice blouse, a big gold necklace and sometimes also a scarf. Some cardigans, but more jackets and blazers. There was one very arty lady from the class of 1958 who wore a small black hat with a feather, red flowy stuff, black flowy pants and way too much eye liner a la Louise Nevelson. But without the extra eyelashes. She was quite a character! Had lots to say about the bad old days.
The house was a very beautiful 1920s I’d guess Colonial revival. In the living room all the paintings were of horses and dogs. In the library there was a foxes head mounted on the wall. Dining room was all dark paneling and beams in the ceiling. There were indeed horses prancing around in the yard.
I had a good time.
^^Y’ know, I just thought about you & that luncheon today! What reminded me was when I started looking at tweed jackets, one of them was from Talbot’s. It was $155. Yesterday it popped up on my computer at $70 some odd dollars and today the very same pop up showed the same exact tweed jacket that was $70 something yesterday selling for $90 today! Boy, that really annoyed me to see that. So then I thought of you and wondered how your luncheon was. So glad you felt comfortable and appropriate in what you wore and that you enjoyed yourself & had a good time! Wonder why some woman had on a black skirt & black blouse and black jacket! Hmmm. Did she have any jewelry or scarves on to break up all that black? Well, mathmom: glad you had a good time and now you have some new clothes too!