Well, but I still want to see what's the goal of having so many speakers in the rear. If you want to have an SPL vehicle, I guess that's ok. But this is bad for SQ because playing any of those speakers in the rear loud will shift the sound stage to the rear, not to mention all the phase and time alignment issues. Another problem is that a typical amplifier has 4 or 5 channels, not six.
Instead of three sets of so-so speakers, I'd buy one solid set for the front. If you want something with lots of bass, consider HAT Clarus. With 7mm of xmax and FS in the 50s, this speaker is great for bass while still offering very good midrange and treble performance. Cross it at 50Hz-60Hz and use subwoofer to fill the lows. Add rear fill speakers once you have a processor to implement surround sound processing.