Hi Rat,
No, I've not found any documented measurements on this subject, but there are so many variables (speaker sensitivity), listening level tastes, source material, etc.
For example, for classical or acoustical recordings where the surrounds are just supplying ambient information, the power requirements for the surround channels would be rather low--a few watts per channel would likely be enough--but for movie soundtracks where the "crack" of a thunderstorm was hard-mixed to the right surround, you might need 75 or 100 watts on a brief transient.
And then you have to consider DVD-A or SACD playback and mixing, where with some rock/pop recordings, the artist and mixing engineer place you in the middle of the band. In that case, high power requirements would be essential, depending again on the nature of the musics and its dynamic characteristics.
Then there's room size, etc. But it would be fun to put an oscilloscope on the outputs to every channel and watch for clipping of the waveform using a crappy low-powered A/V receiver, a well-designed one with better power supplies, a multichannel separate power amp, and monoblocs.
A mammoth project, but if someone's doing a PhD thesis or a paper for the AES, a worthy one.
In the interim, I'd say buy as much power as you can afford!
Regards,
