Total power available to a channel is somewhat dependent on the power supply. The 7075 has a power supply capable of providing at least 525 watts into all 7 channels at the same time (7X75). Each channel is not capable of providing much more than its fair share since you essentially have seven 75 watt amplifiers in the case. Being that most of the amps built by ATI for Outlaw are pretty conservatively rated you might expect to get a few more watts out of each channel at full power. Now for the reality part...the rears, sides and center will never approach the full power of each channel on a continuous basis. The use you have for the 7075 is perfect for what you are doing. Powering the surrounds and letting your mains get more power from another source gives you a little more headroom on the power supply and may let it last longer.