How about getting an old 99-00 Accord Sedan and dropping in an H22A (Prelude VTEC) engine into it? Both will probably be at least $15,000, leaving you plenty to mod with. If you ask me, it's a very respectable sleeper-type and nobody really expects it.

I wonder how much a good condition 240SX and an SR20DET combo would cost; that would be an excellent platform to start on.