Re: Need help picking either 6x9 or 6 1/2 rear speakers.
Instead of spending the money on front speakers, back speakers, and enclosures... I highly recommend getting a set of component speakers for the front that can handle a decent amount of power. Loud comps up front > coax's all around. I've had the exact same highs setup that you are preparing to go with.... and I now have what I am suggesting. Believe me when I say it is a HUGE step up in volume, clarity, and imaging.
SoundQubed 6.5 Pro's DD T2 Tweeters / Phoenix Gold Xenon 100.4
FI SP4 15 D1 w/ Tantric Sounds softies / DC 5.0K
Singer 310 6 phase 2 runs of Monster Cable 1/0 / Exide g78 AGM under hood and XS D3100 in rear
Plenty of deadener. CCF and fiberglass insulation in doors... thanks to the advice of keep_hope_alive they sound AWESOME! :-)