I doubt that you would need a sub woofer, but depending upon the exhaust system you have installed you may need plenty of power to hear anything.
(I do...)
I have two sets of 6x9 speakers. One in the far back in a box from Motorsport auto, and one set behind the seats in WalMart special boxes. If I was doing it over I wouldn't put speakers behind the seats. They seem not to do anything.
The parts you have picked seem to be good stuff. I bought all my components from Crutchfield and they gave me good service.
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