That ends up being a loaded question for me.
Most often, we watch television via Tivo. So sound is usually Dolby Digital, but nothing amazing.
I care most about 2-ch music. That's when I sit down, close my eyes, and allow myself to just listen. I prefer little light and zero other ambient sounds. That's when little differences make an impact (to me).
I care second-most about movies. I LOVE a good movie with an engaging sound track/sound effects. Most are pretty good these days. For example, Tron: Legacy. While it may not be the pinnacle of acting or story telling (I liked it, but I've read several posts where people weren't big fans of it), but it is SOOO much fun to watch on a good sound system.
I never listen to multi-channel music. I don't have the source material and my surround speakers are just intended for movies.
As an example, I'm toying with an amplifier purchase. I really want 7 channels total. My surround is just 5 + sub, but the extra 2 channels power my patio speakers. Those are just ambient music so I'm not picky about the amp. Also, space is at a premium for me, so component depth and height can matter. Anyway, my debate is between a 5ch amp + a 2 ch amp (9b-sst2 + 4b-sst2) or a 5ch + a 3 ch (9b-sst2 w/4 channels + 6b-sst2). Getting to turn on just the 2ch amp for music is a plus (heat), and the height + heat output of the 4b+9b may be less than the 6b+9b. However, I leave my center channel with less power and not identically matched to my L/R.
As for the SP3, there's other things I admire. For example, it will take any digital audio source and supply an analog 2-ch downmix to a set of outputs I can run to my headphone amp, and I think to Zone 2 as well. Less cables required and easier operation (for me at least).
Decisions, decisions.
