Perhaps you're misunderstanding or making comparisons between different spec basis, but without model numbers hard to know what you looked at. Most avrs are going to be within a few dB of each other in any case. The Denon 7200, if you saw one, benched in the S&V test 185w at 8 ohm 1% thd 2ch driven. Doesn't mean it's significantly more power than your Onkyo. Some avrs have dual sub outputs that can separately adjust for level/delay, but otherwise a simple y-splitter is all many of them have internally.