Beyond a certain level, maximum power output (taken by itself) is not a very useful measure. Even prior to the class D era, there were plenty of power amplifiers used in pro audio that had hundreds of watts output, were comparatively cheap, and sounded pretty horrible. Power supply quality, component quality and consistent (e.g. transistor matching), the overall design philosophy and circuit layout and manufacturing quality are all influential. My current amplifiers are the lowest powered (120 w/ch into 4 ohms) that I've had in my system for a long time - and they sound the best so far.
Too Much Power
Please bear with me as I am nowhere near an expert at this type of thing...
I recently read a review of the PS Audio Stellar M1200 mono amps. I was somewhat taken aback by their power rating of 600 watts at 8 ohms/1200 watts at 4 ohms. Made me wonder what, if any, are the drawbacks to that much power? Welcome your thoughts...