Apparently it's useful to point out yet again that Drifter wanted help with "Crossover Frequency Confusion". That confusion about crossovers isn't likely to be lessened by instead discussing the separate and much more complex question of room eq. Randy's reply covers the question asked quite well.
Rob, on your crossover related question, it'd be probably be too much to suggest that "harm" would result from setting the M60s "Large", when a sub as good as the EP500 is available. However, by not setting a crossover for the M60s advantage wouldn't be taken of modern bass management which has been paid for in the sub and HT receiver. The capability of the EP500 would be wasted in part by having the M60s play low bass frequencies that the EP500 is designed to do a better job of. Cleaner M60 response above the crossover is one benefit, less load on the amplifier is another.
On the amplifier load point, however, it should be pointed out that this is sometimes exaggerated in the form of claims that bass frequencies are inherently "power hungry". Of course, basic audio technology is that power requirements are related to loudness and unrelated to frequency. For example, playing a 400Hz note at 80dB requires ten times the power that playing a 40Hz note at 70dB does.
The bottom line is to set even large tower speakers with an appropriate crossover, most likely 80Hz.
