For movies, it is mainly ambience that is put into the surrounds most of the time. Occasionally, there is more activity such as specific pans of jets and such, and sometimes some low frequency effects creep into the surrounds. The surround speakers on a movie dubbing stage do not particularly have any huge low frequency capability, probably cutting off around 50Hz, so generally the mixing engineers do not put such material into them (I spend a lot of my working time on movie dubbing stages). For music SACDs and DVD/As, anything goes, although I would think that most mixing engineers would not put bass heavy instruments into the surrounds.

Generally, I would think that 100 or so watts would be adequate for your surrounds, especially if you use bass management and direct the low bass to a subwoofer. The low bass is where most of the power demand is, and removing this demand relieves your amplifier of having to deal with reproducing this frequency range, thus conserving power.

That being said, there is no downside to having 200 watts driving your surrounds. You will probably not utilize all the power, but on the other hand, it will not hurt to have it.

[This message has been edited by soundhound (edited May 16, 2003).]