Having sold 'mass market grade' components for the last 6 years, I am intimately familiar with this situation. Gonk is most correct, underpowering a speaker is much more detrimental than overpowering. Be sure to do yourself a favor and get an spl meter to set the levels of your surround channels. Having sold the entire Polk line, I can attest to these speakers headroom. The 755 will not cause you an issue unless there's a large ammount of distortion in the signal (given that your levels are set properly).