dbc9todd, you can substitute similar things in the management degree (ie 18.700 instead of 18.06/1.00, 6.001, or some combo of the new 6.0x courses/6.041 or 18.440/ect), so no worries if your dreaming of a math-buisness combo or something

(not too much paperwork either)
to the OP: if I can go out on a limb- I think 18.06 is a little easier than 18.03, so I'd say take 18.03 in the fall and watch matuck on OCW. I know some people who did that pretty successfully, and kinda wish I had.
to anyone planning to take an 18.02 in the fall, look into 18.023- it was possibly the most entertaining course i've taken at MIT.