Cobras are garbage. I drove a few when I was shopping around for a new car, they are fast..but it seems like a 5 year old put it together. Dont slam the door othewise the door panel might fall off, and when you get on it, all the plastic on the dash squeeks soo much you can't hear the engine.
S2000's are overpriced, and under powered. For $25,000 I'd want a car that can at LEAST hit a 13.99. They are heavy, small, and its really hard to get more power out of them without spending a million dollars.
Good luck finding an STi for less than $25k.. If you do, its going to be ragged out like a dirty whore, and probably have 50K+ miles. I wouldnt spend money on a used up car like that..
Supras are in the same boat as an STi, to find one less than $25,000 would take a long time. You can find them all day, but they are raggeed out, have 100k+ miles, 9 out of 10 are auto's and did I mention they are ragged out?
NSX's are probably the worst thing you could buy for that kind of cash. Not only would you spend every cent, but you'd get a 1991 with 170k miles, ragged out interior..ect Just old. No one should pay that kind of money for a 15 year old car... no way.
IS300's are nice, especially if you get the manual transmission. But, they arent fast enough for me... you have to make your $25,000 work for you..it's a lot of money to spend so spend wisely.
If I were to spend $25,000 on a car...I'd probably get a used, unmodded, clean, low-miles, Evo 8. They are well rounded, fairly cheap compared to the STi, solid as a rock and you can make sick power with simple cash and simple mods. (unlike the STi, you'll have to have a reflash for the ECU if you get an intake, downpipe and exhaust)
I was a signature away from buying an Evo 8, but when I looked at it on paper..I decied to build a Civic. Faster than all the above, cheaper, Honda reliablity..best of everything. Now, granted it's still a Honda Civic and it doesnt have a huge racing pedigree like the Evo, Supra, and the STi but its fassst.
It's your money, think about what you'd like to own and drive everyday.