If you want to "wow" people with it:
The motor from an air cooled gsxr 1100 is a direct bolt-in swap.
You're talking like 140hp and over twice the torque you have at this point.
THAT is a swap worth doing. A used 1100 engine is a bit hard to come by, but you can get one for about 800-1000 bucks.
And if you want to turbo something, a Triumph speed triple or Daytona 955i is the thing to do it to. It's like the motors were designed for it.
mmmm.... turbo speed triple....
Check out katriders.com, a few people have done the 1100 swap. The katana 1100 and bandit 1200 engines also fit, but they don't have as much power as the gsxr 1100 one does.