Yeah, a good friend bought a stock as a rock auto S14a for exactly 15k as well.. I took it for a drive and its awesome. Luxury car with a bit of speed. A few minor mods and the thing will fly.
I think you could, if you're lucky, find an R33 for under 15ish and close to your price range if thats your thing.
And yeah, fmx is right, look into insurance before you buy. I nearly had to sell my car because noone would insure me, and the one company that would, as soon as i started listing the mods, they told me to fuck off. Im 19, 1 point lost, no criminal record, no crash history etc. Luckily Just Cars opened up and i got myself 3rd party/fire theft for $600. Full comp is about ~2500.