i can't say i didnt upgrade my rear speakers. but i had my fronts removed for a few months (ordered some that died and had to send them back) so all i had was the back ones. it was horrible. hard to hear at speed (w/ windows down i couldn't hear CRAP)

why only upgrade the front? because YOUR driving. how often do you have a completely full car? not very. most people drive alone, the majority of the time. I'm not saying DON'T do anything in the back.. my rears give a good mid bass... then subs for the low end. But if i removed them... i wouldn't be too upset either.