[H23A1Lude]

If you want a swap, go for an H22. Check out preludepower.com, look around. Azrace+machine recently made H22 mounts for this car.
An H22 is something like 20 pounds heavier than the B20. And it sits really far back in the engine bay.People have done a b16/b18 head swap. From what I understand, it's the same thing as an LS/Vtec, but you have to move/create 3 bolt holes. However, this isn't as beneficial as you think. These motors have a very strong tendency to throw a connecting rod(#3, usually) if revved over 7000. And that's just a pain in the ass. So you'd need custom cams for the head as well. You could also boost the B20. People are running 300+ on stock sleeves, they have thick iron sleeves from the factory, and stock internals can take 220 at the wheels, 240 with a perfect tune. But boost always has its problems. IMO, I'd do the H-Swap.