Just focus on your front stage for now. Audition as many speakers as you can, decide what you want, and take a lot of care and place a lot of attention to detail in the install, as that will make the most out of an audio system.
Disconnect or remove the rears altogether and acclimate yourself to a front-stage only setup for a few months. If you still feel you want some rear fill, then get a decent set of coaxs and power them off the HU.
Disconnect or remove the rears altogether and acclimate yourself to a front-stage only setup for a few months. If you still feel you want some rear fill, then get a decent set of coaxs and power them off the HU.