I just read back thru your posts. If you already have a sub 15 " and shakers in your couch... then I would suspect that your new AV receiver is not providing the power you need (crave?) lol I have a Boston AVR7120 an exceptional 7.1 with gobs of power and I like my home theater sound better than going to a pay " movie theater" 95% of the time.
Just curious..... are you sensory deprived?
Just kidding lol
I still think the DV64 would be best. Does your reciever have an equalizer or analyzer mode to set the fronts and center up? A lot depends on room size also, but 15" dual mains might get very muddy and also sap power adding lots of IM distortion also.
I am using dual BIC (PAS 10's with separate 120 watt amps) 10" subs.... one behind each of my bi-wired DM603's