Well I can't speak specifically for the 3806 but I had the 3805 that I bought back in March 05 and before that I had the 3802 and 3803.
After having the 990 for about 6 months now, I would absolutely never consider another Denon again.
I listen to most of my music in 7ch stereo and with the Denon's I experienced a muddy center channel sound and could not figure out why. I first experienced the problem when I upgraded to to the full 7.1 Polk Audio LSi series speakers with the 3803. After troubleshooting everything the problem pointed to the Denon 3803. I pawned that one for the new 3805 and the nasty center channel sound was still there. I ran across a few in the Polk forum that were expriencing the same problem and they recommended trying another brand receiver and sure enough, with a test yamaha RXV-2500 the problem was gone. The yamaha was bit underpowered for my 4 ohm Polks so that began my search for a new receiver which led me to the 990.
There many, many reasons from my experience the 990 outperforms the Denons. It wins hands down in every category, especially in overall sound quality and don't forget the outstanding customer support from Outlaw, try getting that from Denon.
Hope that helps you out a little.
_________________________
"One Shot, One Kill" Semper Fi