I use the setup you just mentioned already and I love it, Im actually running all four door speakers off of two channels for a lower ohm load and more power, and then my subs off of the rear channels. It works well if you dont ever fade your door speakers. I do have a remote gain control on my subs and love that, because I listen to everytype of music and bass can vary so much.
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Lucas S. Starkvegas, MS