We have to know what engine is in there to start with.
Oh and BTW, Id never put a CA18DET in a 2000 car, I mean, c'mon man.... way too old stuff.
Now, if its an SE, options are SR20DET or SR20VE.
GXE, I say go turbo, it'll be a major pain in the arse putting in another engine, and turbo is the only way to get descent power if your looking for a big change (since you are, because you talked about swaps).
Altima engine.... hope you dont mean V6, cause forget about that.
And as for the "Spec V", btw, its SE-R engine, not spec V engine. And its called a QR25DE.
That would also be a major pain, but... its doable, since you can purchase all the stuff off a totaled SE-R to transfer over. It'll still cost way more than just going turbo IMO.
any questions, just ask away, oh and check out
www.npclub.com most answers are already there.