Rear speakers are just awful that's all. They don't change/add anything significant, especially once you have nice front mids and highs. And that's why I'm saying 8 inch subs. You widen the holes where the 6x9s were, drop in some 8 inch subs, you have your bass. You'll never truly have "a little bass" with just coax speakers. With that, run a stereo 2/4 channel amp for the front speakers and a mono d-class amp for the rears 8" subs. With a d class you'll be able to just drop it underneath the rear seat, and if you want to get fancy, you can drop the stereo amp under the center console. Totally hidden, totally upgraded sound.
