set up
I had on order the 663 - but it was taking forever - so the dealer gave me the 863 for cost (sweet). That said, I've fiddled with the settings (the are the same as the 663) quite a bit, and for my taste, I honestly found that the pure direct mode gave me the best sound for music - and now after a few weeks of ownership, that's basically all I listen to.
For tv and movies, I generally have it in 7 ch mode. As for the settings, I found that just making sure that setting the speakers to large v. small or vice versa is where I noticed the most difference. I did set everything else up manually as well - can't recall the settings off hand - and have not tried YPAO yet - though you can also manually set the speaker balance and distances as well. I can say that did help quite a bit over the default.
And so far I've found this to have plenty of power - though I seldom go above -25db on the dial.