depends what kinda much you listen too.
if you have subs and plan on using them, you could get some infinity kappas. they have really good med to high range sound, but not real good bass (which is what the sub is for) if you dont plan on using the sub, the new Alpine Type-X Componets are very nice (little pricey) Polks seem to have very good quality sound aswell.
I've had infinity kappas before, and they sound awesome, but just didn't have a whole lot of bass, so i got an infinity kappa perfect sub, and they was an awesome setup.
on my celica, i'm planning on getting the alpine type-x componets w/ 4 channel alpine amp, and just do that. it will sound real clear and have decent bass.
cheers, hope i helped a little!