Doesnt have to be that expensive - system i put together in my other car cost me bout ?600 and sounds crisp and clear to me.
Mainly Kenwood, which aint the best but its not bad.
12" sub
7 x 10's shelf
6 x 9's in doors
3" mid/tweets in dash (JBL's)
Jackson 4 ch amp (the weak link)
Kenwood h/u radio/cassette. 6 disc changer in boot.