There is soooo much negative bullshit in this thread from ignorant honda people it's astounding.
FrodoGT and omgwtfbbq please do a little research before stating your "opinions".
OP do a little research on www.rx8club.com and i'm sure there are several S2000 sites out there as well.
Go to Carmax or something and test drive both and then make a decision
there is ton of aftermarket parts for both cars.
The RX-8 will be harder to get more power out the engine without spending money on FI.
Both cars have reliabilty issues.