I have a NAD 902 power amp (90W bridged mono), and a Paradigm SB-100 passive sub that will soon be surplus. It seems to me that I can take the "sub out" from the A/V receiver into the 902, and use that to drive the sub, giving a "powered sub". Switching the polarity at the speaker outputs should be the same as a 0/180 phase switch, and the 902 has output level adjustment. Is there any reason why this would not work?