yea i bought kami's 7k, cant remember exactly what i paid but yea was around that price bracket, it was worth every dollar anyway, had a very noticeable effect running with the TD05, held boost higher in the rev range and a much more aggressive tune. i ran 15psi every day with it, and for a short period even ran 17psi, though i wouldnt recommend that haha, was pretty quick though.
to give you an idea, on basically a standard v2 wrx 20g setup, with TD05 and the 7k ecu my car dynoed 167kw at rear wheels. i had the factory downpipe in so didnt have trouble with boost spike.
definately find yourself a 7k over a 6k, may just take a little while to find one, i on-sold mine for $200, now im running a posssum link.