you might be able to get an all kicker ( maybe kicker competition ) system, 12" subs and maybe a kicker amp
or you could get some JL audio 12's and a decent amp. should knock for a good while
i worked wit the same budget in my first ride and had some 12" super blue subs, fossgate amp and pushed it for a good minute.
you could get some JBL's, they cooh but in a galant it might rattle too much
you could get a real decent system in there if you put it together right. it all depends on ur taste and what you going for
all around sound, or just somethin' that knocks good until ur budget gets better