Does the Yamaha sound bad? If you kept it, maybe pick up a used Parasound HCA1200ii - I just saw one on that list site by me for like $500. Then use your Yamaha to run all the surround speakers and the Parasound to run the Monitors. Then you can take the money you save and get an REL subwoofer. The new 12" home theater subs are pretty reasonable...
Just another option, not saying it is the best one.
-Geoff
Just another option, not saying it is the best one.
-Geoff