Voted RX7.
I'm going to catch **** for this, but I really don't like Nissans at all. Only Nissan I've enjoyed has been the one the guys at CMC run. Gutted, megasquirt, built to turn not drift, scary light, incredibly nice guys too.
The Porsche I don't really know too much about, I'm not sure how money pit they are. They look cool enough though.
The RX7 would be my choice just because of the v8 swap possibility I talked about in the craigslist thread. LS1's in them don't affect the weight distribution at all. The poor mans LS1 is the 5.3 vortec which is only 100 pounds heavier and 10 less hp with comparable accessories. Get an NA or turbo one, run it till it pukes, v8 swap, OR pull the rotary and sell it to recoup swap costs. Yeah, a swap is a lot of work, but a GM v8 in a tiny car is just plain awesome. A cheap already swapped one on v8rx7 message boards will usually cost less then the parts that go into them, problem is you don't know if the swap is done right or a hack job.
The rotarys are interesting, but they're moon tech to me.
Check out this twin turbo FD vacumm diagram!. Granted a single turbo FC or an NA wont be nearly as scary as that. If you keep the rotary, you've got plenty of RX7 message boards for support + parts. I can't comment on the rotary reliability because I don't really know and I don't want to talk out of my ass. I do know that they drink more gas then piston motors and that megasquirt ECU's are pretty much plug and play on them now. They're basically the miata's ancestors anyways, just with a hard top (or sometimes ragtop) and funny motor. Just like any 20 year old car though, there's bound to be good ones, and ones that are basket cases.
Another option. BMW E30. They're plentiful and cheap to buy, can be had in coupe or sedan. The I6 motors are wonderful. RWD (unless you get an ix, which I'd avoid as parts are retarded to get for them). E30tech has boatloads of info. People turbo them for cheap. You can combine different motor parts and make strokers. You can make them turn. A CMC guy runs a rwd e30 and it's on rails basically. A buddy has an e30ix + parts ix and it has reached moneypit status because of how rare the awd one/parts are, but the kid is a BMW encyclopedia.
I'd probably be pushing my luck if I suggested a mustang on here, but I know the most about those.
If you do decide on a make/model you want to seriously look into, I'm sure people on here can chime in with what to look for what to avoid. I'm more then happy to help aggregate info and buying guides.