Randy,

For the benefit of others, I just want to keep everyone in the loop on the discussions we've been having.

I have my 600 set 6dB higher than my mains. When I switch from stereo to direct, I don't notice any difference in the bass. This is due to the fact that the mains contribute very little given the fact that I have my sub set four times louder than my mains. I think the math works out to a gain of 0.8dB with the M80s on large which is an inaudible difference.

Since you have your sub's SPL set to the same level as the M80s, you are at least doubling your output (3dB) in direct mode.

Have you tried turning up the gain knob on the back of the 600 (ie. not just through your amp)?

I hope one day we can start enjoying the music .