Here's why I'm leaning against buying a Denon:

1. I just bought my Sony 4 months ago, and really like it. I don't want to pay $$$ for a Denon right now -- I made that decision then for the same reasons I would now. The Sony serves my needs for many years.
2. I don't want to be running two receivers. It's much simpler to have a dedicated amplifier with zero features except to amplify. The Sony can handle everything else through the preout RCAs. I'm leaning toward one from Russound or Xantech. While they're expensive, at least they're the best at what I want them to do -- drive my house speakers -- and don't add any extraneous features.
3. If I were to buy the Denon, then split the signal via a speaker selector, I'd be paying roughly the same or more as buying a dedicated amplifier, but the speakers would get less juice. It seems to be an increase in flexibility I don't need.