rsx base and the civic si are the same exact motor, with 2cam lobes that make for better fuel effeciency(spell check). the rsx-s is no doubt to be better, all that matters to this poor man thats asking us for a favor and give him some info, i like the rsx personally, cause i like the hatch look and by looking at the si i am like is that a hatch? micro minivan? and i wont be used to that shifter, but i heard the original shifters was like that. hmm i dunno well the si isnt all bad for others but to me when i take that threw the twisties i think?"wouldnt i tip that sh!t over if i go to fast?" okay wel my conclusions states that i am getting a rsx if i were u, but now if i was me i trade in my em2 (04 civic) for a rsx-s