u can do a d16 Si block, or a zc block for not too much more install in just as easy as installing the d15, in order to maximize ur hp potention ur gonna have to do a swap to mpfi, instead of the dpfi i believe the lx had but im not sure what the lx came with, hopefully someone else will chime in with more info on that, but id suggest using a better block with more hp, difference is only gonna be like 50 bucks for like 30 more hp, i know of no cheaper way to get more hp than to go to a slightly larger block if ur already planning or in need of replacing ur current one