this is the wrong crowd to be asking, ever been to mr2oc.com? personally i am going to be getting a 4agze off ebay and im going to rebuild the motor and twincharge it. but the mr2oc has forums for each type of swap, and if theres a link in there for the twobrutal site, which has a lot of good info on the swaps. but heres my opinion on some things:
7A-GE doesnt exist but that idea (unless you can find one thats been done) requires you to either buy 2 engines or hunt for a lot of parts.
4A-GE 20V cost alot more to make a 20v go fast than to make a 16v go fast.
3S-GTE i like this swap, nothing wrong with this one that i have heard of.
you could even do a northstar V8.
i personaly like to stay in the 16v 4age world. their is more of a fan base, so more performance parts available. plus the 4agze has a strong block you can push alot of power through. but yeah defiantly go to those other forms and get educated on the different engines and their pros and cons