The easier way would be just turbo what you have. The harder way is GSR and then turbo. The hard way is H22A and turbo. The hardest way will be a HEMI.

I have talked to a Honda guy, which had a B16A and B18B. He says the HP are about the same, but the B18B pulls better cause the extra displacement. The B16 make about the same HP only because it revs more. So do not limit yourself with less displacement. Another guy told me LS/Vtec with turbo is the way to go, but never driven one so I cannot help you much with that.