25-30 will get you a lot of skyline, check out the FS section on this site, it is really up to you...........you can get R32 GTR's, R33 Gtsts with mods, and maybe the odd desperate to sell R34GTT.
I'd think in another way, 25-30 will get you 250-300kw at the wheels = $100/kw. Lot of power for a guy coming off P's, i'd probably look for a 240kw unit and save some $$$ for head units, gauges, zorsts, tyres, bling and insurance etc.