Let me caution everyone to keep in mind that these are just my opinions. I'm sharing with everyone because I have, in the past, wished someone would do what I'm doing and post about it. I finally just got up the nerve to do it myself.
I would strongly encourage anyone looking at any of these receivers to do exactly what I'm doing and test them for yourself. All the reading in the world is no substitute for actually hearing/seeing it for yourself. I don't have an agenda over which setup 'ought' to sound best, and so I'm trying to be as impartial as I can. But I'm only human and don't pretend to have golden ears. I just know what I like. I'm sure there's more than one Onkyo owner around here that's cursing me for being negative about the 876. Sorry about that, but it just doesn't work for me.
I will freely admit that I did not spend hours tweaking the Audyssey setup, and so it is very likely
that is is better than I say it is. I went so far as to calibrate it to 3 listening positions (I know more is better), and then to tweak the crossover points. Audyssey wanted the M80's and VP150 as full, with the QS8's crossed at 70hz. I had read online (AVS) that it's best to set all the speakers to an 80hz crossover, which is ironic, since a global xover is one of my complaints about the SC-05. I also played around with which EQ mode it used, 'MultiEQ XT' vs 'Dynamic EQ' vs 'Off'.
I was not impressed at all with the 'MultiEQ XT' mode. It sucked all of the midrange out of the setup and did something that completely killed the soundstage - speakers became very easy to pinpoint. The Dynamic EQ was what I used (per AVS recommendations) for most of the testing, unless I was using the 'Pure Audio' direct mode or the multi-channel in, neither of which use any calibration (AFAIK). But for PCM signals, yes I tried both Audyssey on and off. It certainly changed the sound, but I can't really say that one way was better than the other. I could tell that Audyssey was trying to enlarge the 'sweet spot' at the center of the couch, but it was not really all that impressive.
It genuinely pains me to say it, but neither MCACC nor Audyssey seem to really be doing much more than what I've been able to accomplish with an SPL meter, rugs/drapes, and some speaker positioning tweaks. Maybe my room is better than I think it is.
The most revealing test for me was the pure, analog-input, no processing, SACD sound. That's where the difference between these two was most apparent.
The 876 is heading back to Amazon. I'll probably have to pay the return shipping on it but that's ok. It's fair and worth the peace of mind to me. As soon as Amazon issues the credit (about a week, in my experience), then I'll re-evaluate the situation. I've got a month to decide on the SC-05.
As it stands right now, I'm leaning
towards returning the SC-05 too and waiting until the UMC-1 is released. Or I may just wait until the 3808's replacement is released, considering that it's almost 2 years old at this point. Or I may just swap the SC-05 for a 3808 and give that a shot. I've read through the manual and it is an extremely impressive bit of kit. And it's clear to me that it has a huge following around here. My only problem with the 3808 is that the best price I've found is about $1,400. And for that, I could get a UMC-1 and an XPA-2. Or a UMC and Oppo's BR player. Too many options.
Though my wife's suggestion is that we start looking even further up the food chain. "What about Marantz or NAD," she asked last night. "Those are going to be closer to $2k, if not more " I replied. "So?" she asked. Oh bother.
Not exactly sure where this will end up. All I know for sure is that I need a few days to rest my back after hauling around 60+ pound AVR's and amps for 4 days.