well i'm not sure how well that would work you're probably better jsut getting the ca or your probably better off just getting a ga16de besides you can get a turbo set up for the ga as well as the ga heck you could even go with the sr20de even who knows i'm kind of thinking about getting a new engine myself i mean heck i saw this one http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7955366645&category=33615ng
and i had found the turbo thet turbo set up for fairly cheap as well...but sadly i wont have the moeny to do anything for a while well good luck whit what ever route you take.
Lots of cheap torque? Not likely, but yeah a motor swap might be your best course of action depending on application and the amount of $$$ you want to put up. Set some realistic goals, determine your budget, and search around these forums, you'll more than likely find a solution to your needs that has been discussed before.
u can try lookin in teh bargain nes or somethin for a smashed or just plane cheap pulsar se to get the ca18de plus u get all little goodies that can bolt onto the sentra, brakes, suspension, even seats