If your not worrid to much about the price of things, then you need ask your self dual cam or singla/. vtec or non? A good dual cam engine would be the b16a witch is what i like cause its good power for the price. Also a b18c1 would be a good engine, but its a little high priced for not much more power that the b16a. Si vs GSR. But another good dual cam would be the ls engine the b18b2 its non vtec, but its a good power increase from a single and its not as pricey as the dohc vtec engines. You can also easly boost it with stock internals and it will hold. But for single cams i'd only run about 7 psi boost on those, and my top two favorite d series engines are the d16z6 and the d16y8, the y8 has more horse from factory and better torque. but I think the z6 has better compression. But you could always get a freak engine and put it in, like a k series or h series. k series is about a 5 grand swap and the h series is not much less.