Autotek makes a amplifier that offers 75 x 4, or on up to 150 x 4, but if you would run the 6x9's off the HU's rear speaker outputs, which should sound okay, you could then purchase one of their x-class monoblocks that should provide the meaty sound you are looking for. The power requirements of the 6x9's and the 12's are vastly different, that is why it is hard to recommend and amplifier to run both sets.