Gonk seems to have the right idea with what I was asking. I was kind of nervous about going with a larger amp as the center and surrounds are rated to 175 and 125 Watts of input power(both are 8 ohms nominal, 4 ohms minimum). I could go with the more powerful surrounds that can handle 300 watts at 6 ohms, but this would cost more. I'm all for cost effectiveness as I'm sure many of you are too.

The 4 ohms min is what gets me going about using the 770 or 755. 300 Watts into 125 or 175 recommended seems to be kind of far over. I would not be playing at extremely loud levels, but I would like to eliminate the chance of overdriving them as much as possible.

This leads me to another question, with the resistance ratings of these speakers, will the amp always try to output at 4 ohms? Or will it be a little lower? I realize that technically the resistance is not entirely constant, but on average, what will it do?

Mr. Sandman, I know doubling the power will only give 3db more, but at the same volume level the sound will come through better.