Is it necessary to keep your rear speakers when setting up a nice system for sound quality.

I've been thinking of just running front components with a 10" in the rear. I remember reading a while back that upgrading the rear speakers was a waste of time with a sub in the trunk and decent components in the front. Is this true?

ANd if true is it possible to bridge the speaker outputs from the head unit to just run all the power to the front components instead of giving some up to the rear?

Hope I'm clear enough in what I am trying to do.