Never had a chance to compare both side by side. The MA 6600 being a newer model with some very nice features which one can operate via the remote control as well, such as the defeat-able tone controls, led lighting, along with the optional tuner with HD makes for a very nice unit. I don't think you can go wrong either way. I do own the 6600 and love it...
McIntosh 6600 vs 6900
Does anyone have any opinions on which is better sounding. If you happen to think one is better, why is that? Thanks