I think 8.1 implies one of two possible scenarios:
1) Front L-C-R, Rear L-C-R with alternate surround L-R speakers for music (i.e. monopoles instead of dipoles)
-OR-
2) Front L-C-R, Rear L-C-R, and a front L-R effects pair that is elevated to give height information. A 10.2 system would add a Wide Front L-R pair and second sub. If I'm not mistaken, Yamaha makes an upscale receiver that powers front effects speakers for 8.1.
8.1 almost certainly demands its own room, unless you want your living room/den looking like an AV store.
