Its good to here you have some experience. A stock sr20de has about 150hp. so its got a bit of power, not huge gobs of it but enough. Ive driven a corolla with one and it fairly flys. Not as quick as a turbo but still pretty good.
I dont think you will have too much luck finding an fj20 for much less and ca18det's are getting up around 3 grand for a front cut.
Will you be allowed to drive a turbo charged sunny on your L's Or P's?
Maybe you could consider an rb20det? OR for similar dollars you could look at going for a 1jz?!! That would be my pick for value for money, and you can pump some serious reliable power out of them. Only thing is the manual version is a fair bit more expensive than the auto(aren't they all) but the auto will cop some decent power and you will be able to keep both hands on the wheel! I dont think it would matter, it would still smash any SS or xr8, unless of course they had spent mega dollars on it. It could be a bit of a squeeze but if you can get an rb into a 120y i say Y not!
What do you reckon?