Thanks to all for your advice! I am copying all into a document so I can start researching and be ready when the time comes. Hopefully that time won’t come when it is 95 degrees out (Murphy’s Law and all…) 
I have an older system, 1998, and one contractor told me to get a new refrigerant system, I’d have to replace not only the compressor but the copper coolant tubing and the coil in the air handler. The only thing I wouldn’t need to change would be th ductwork. The whole cost would be close to what I paid for the original installation.
At that price, the cost of limping along and paying a few hundred every year or two for repairs is attractive.
But there is the thought of the continued use of environmentally bad refridgerant. Balanced a bit in my case of burning pellets and keeping my winter thermostat at 58 degrees.
That said, I read that upgrading doesn’t necessarily have to be as total a retrofit as this one contractor told me.
But it’s hard to find good information.
Be aware that I think you can still buy R-22 air conditioning units, providing they are shipped from the factory without any freon in them. This is a loophole in the ban, and of course it has the environmentalists hopping mad. The problem with replacing a freon condenser unit is that you also have to replace the coils, and sometimes because of space limitations it’s not just a matter of popping out one set and putting in another. It can be really expensive.
So make some calls and ask around, look on the Internet and see if you can find an R-22 unit without freon, Then just buy the freon to go in it. The price of freon was sky high a few years ago, but I think it has actually gone down, although it is likely to rise again. The above presupposes that the problem is with your condenser, of course.
Also, you may have already done this, but you can get quite a bit of improvement by completely shutting vents on rooms you don’t use and shutting the doors.
A couple thoughts…seconding make sure your have the right duct work.
Re Noise: if the sound is from vibration you might be able to have it fixed (I think they use cushioning pads).