If you are in the market for an AV Receiver than this new guide from eCoustics might be of help.

Quote from the AV Receiver Buyers' Guide: "Don't obsess over small differences in power output. It takes a doubling of power to make any significant difference in playback volume. Thus, if you had a receiver with 50 watts per channel, you'd need to go to a model with 100 watts per channel to get a 3-dB increase in loudness, a difference that is just "slightly louder."
Differences of 10, 20, or 30 watts per channel are just not significant in receivers rated in the 100 watt-per-channel range."
Read the full guide on eCoustics.