if you are serious about sounds, try theese for a start , hold a 6'' speaker and are very VERY well made......

companys called audioscape , the piccy does not do them justice , prices are from 120 up to 180

my cars going in for a 3 way speaker system next week, thats a 6'' a 4'' and a tweeter on the a pillars

if you are handy you could make your own baffles and then use a much bigger speaker , you WILL need to chop the standard metal basket about though if you want to get bigger than a 4'' driver

hth