For your budget I reckon you're better off getting something that is already a quick base car. Adding turbos, engine conversions, brakes, suspension et all will chew up your 10k quicker than you can blink.
Something like a S13 (although, I'd find one SR powered) or a 32 or even a crappy condition 33 gts-t would be the go in my opinion. Six months ago I bought a 32 gts-t with a CAMS cage, race seats, harnesses and everything else required for the money you're talking..... search MY105 and disregard the asking prices, it's a buyer's market, and just kick them in the balls and make an offer.
There is always the possibility of getting a race/rally only import, one you can still drive to and from track days etc..... I've seen many good S13's for around 7-9k that would be perfectly suitable, heck a mate just got a great Series 6 RX7 in himself with suspension, big single turbo etc landed for 12k! Best thing is, if you don't chase big HP, most of the Jap stuff doesn't need brake upgrades etc.... thats when you start spending the money.