Mate that's a sweet car you got there.
Since I have it next to me, according to a book called "Toyota MR2 Performance" by Terry Heick 275whp is the upper limit of the stock 3SGTE for the US engines. You could prob get away with 300 if it's gen 3 motor. After that if you want more power everything gets really expensive for balanced upgrades, not just engine.
For 7k I'd prob get good service, exhaust, sussy, tyres, decent pads/fluid, water injection, intercooler, strut/sways and hit up the tracks :D
CT20B is a good tubby from what I hear should be good for your power target but someone else should really chime in since I don't have one lol let alone a working MR2