for head unit- you can try( alpine,kenwood,
eclips),etc they make great cd players
for speakers- you can try( kicker,jLaudio,
alpine,rockfordfosgate) ,they make great componet
sets. for amps you can go with (kicker,precision power,rockfordfosgate), they make great 4channel
amps with built in crossover
for subs you can go with (kicker,JLaudio.bazooka,
rockfordfosgate) they make great sub boxes and
bass tubes the choice and cost is up to you