Nick, the question about how much maximum power capacity that your father would need would depend largely on how far away he sits(more significant than the total room size), how loud of an average sound level he uses and how wide the dynamic range of the source materials that he listens to is. It's unclear why you think that "headroom" with the 7125 would be significantly more than with the 3808, but in any case only enough headroom is needed as would be used at least occasionally. Unused headroom is simply that: unused.
