I don't see any reason to worry about it being too much speaker or power. The RS550's are not much different from the Paradigm Studio/60's I have in a room that is 23' wide, a little over 17' deep (with the listener about 9' from the drivers in the front speakers), and 8' high - a smaller space than the one you describe. The Model 755 is also not much different from the amp setup I'm using (M200's for my mains and a Model 750 for center and four surrounds). I had the same speaker setup in a smaller room before (11' wide, 19' deep with the sitting position about 8' from the spakers, and with ceilings that were just under 8') with the Model 750 driving everything except a surround back speaker and never felt that it was too much.