go for the rainbows... I have them in my mk3 and they are superb... they'll go as loud as you can take it
they are quite high pitched though so i'd go for ones with the 'kick' in... I don't have a sub fitted yet but when I do then things will be evened out a bit...
even so... they are just an awesome speaker
don't go for components in the rear - only the front otherwise you'll end up with a tinny noise in your ear
