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.
CDT carbon fiber 6.5" mids & DD T2 tweeters on a Polk Audio PA D4000.4
SP4 15 w/ Tantric SHD softies on a DC 5.0k
2 runs Monster Cable 1/0, SounDrive rca's, Singer 310a 6 phase, Exide G78 under hood XSD3100 rear, plenty of deadener