I mostly listen in 7 channel surround mode, but when I sit in front of my M60s, I usually change the receiver to "Pure direct" and only listen to the mains, no sub. I find that the bass is tighter and the imaging is better that way. I find that when listening in 2.1, the image collapses a bit... I don't know why. But, then again, I rarely get involved in critical listening sessions.