I think, that the imagination that all instruments and vocals are supposed to be in front of you is not allways correct.
A good example is the song "Bohemian Rhapsody" which was remixed to 5.1 in these days. Queens guitar player Brian May (who has also directed the new 5.1 mix) said, that this song actually sounds more natural in 5.1 mix and, if they had the technology in 1975, the whole album would be mixed in surround sound. They had actually troubles how to mix all the vocals in the "opera part" (at some places 256 voices at the same time) just for 2 channels so that it sounds as monumental as possible.
It should not sound as if 256 Freddie Mercurys and 32 Brian Mays would sing and play in front of you, it should sound as if you would be in a some .... dream world. (with a 100000$ Burmester surround system
)
So, i think, it depends on the music whether 2.0 or X.1 The artists (composers) should decide, how are you supposed to listen to their music. I like listening to good music suitable for surround mix on a good surround system
On the other side, if you are listening to a jazz peace with one small drumset, one piano, one bassguitar and maybe a saxophone, a 5.1 mix is not a good choise...
I hope you understand what I mean. I have troubles with my bad english.