I have ann E46 now and used to have an E36.
From what I've seen, most of the driving instructors here in the Puget Sound area have E36s. They are less expensive, ton's of mods and still a kick ass car. I upgraded to get the SMG transmission which is a love it or hate it kind of thing. It is totally great to drive around Pacific Raceways and never have to take your hands off the wheel to shift.
If I was not dependent upon the SMG and I was building a track car, think I'd go with a 96-99 M3.
If you want the best and can spend 60K, then go for a new M3.
Whatever you buy, MAKE SURE you take the BMW Car Club novice driving class next year.
http://www.bmwpugetsound.com/driving_schools.html