The 811S does fall behind in 2ch music performance. But you have to consider what it's falling behind. Most people that comment in the 811S musical inabilities are comparing it to Harman Kardon, Marantz, and other higher end receivers. I find the 811S musical reproduction to be adequate, but i'm...
I would have to reccomend the D811S. The $75 or so you would save would be well worth the fact that you'll be able to move into 6.1 or 7.1 whenever you decide to. As someone else mention, the 811 is much more "future proof". It already has the most current processing technology (except logic 7...