While there are a lot of multi channel recordings out there such as the suggested Eric Clapton Crossroads, any decent AVR or surround sound processor can already simulate full surround on any standard stereo recording. For music, you are not sitting on stage among the instruments, so back we go to the surround on the multi channel recordings just filling in the ambience of the venue. When we play simulated surround with regular stereo music there seems to be more content from the simulation and the channels are carrying more actual music on the surround channels than an actual recording done in surround. Both are good IMHO. If you want music from all channels your only limitation is your system. If you want to feel like you are sitting in the middle of an arena, the actual surround recordings would matter more. In any case I doubt studio recordings done in multi channel would be much better than the computer inside the AVR would create. I'm playing more and more stereo music through the surround sound processor these days, and it's pretty good. I would say this is also dependent on your system having full range capabilities for all channels or close enough.