i say go with a b16a there are a whole lot of options to do with them and u cant go wrong with the 8200 redline. my buddy has a 89 crx dx with a b16a in it and he can take most cars on the street. if u got alot of money layin around get a a b16b thats my dream engine . the b16 is a very strong motor i suggest staying away from the b20 unless u have alot of money to throw into internals (new sleeves exetra). the b16 is a very easy swap to do but u have to get some ls rotors n calipers n brake to fit the axles and to be able to stop. anoother thing if u go with a dohc motor like the b16, b18 exetra i suggest getting sturt bars right away and if u have the money get some new suspension. ( control arms, use a hf sway bar, struts springs ) but if your crx is a 90-91 si u probly wont need to get (control arms, struts springs) but put a hf sway bar on not matter what.