I'm a little late to the game here but could not resists weighing in. There is no doubt in my mind that a very good recording which is available in a 5.1 and 2.0 mix, is more enjoyable in 5.1 at any systems pricepoint over say 5K (or even a bit lower). For example, the Nordic 2L recordings come in 5.1 96/24 and 2.0 192/24 and the MCH mix wins hands down on any half decent surround system.
Think of it like this. You have say 20K invested in a good 2 channels system, and have 10K more to spend. Your options are upgrading your 20K 2 channels system to a 30K 2 channels system, or spend 10K on a center channel, pair of surrounds, 3 channel poweramp and active sub. Your 2.0 channel upgrade is deep into diminishing returns territory, while your 2.0 to 5.1 upgrade is a huge net system improvement. The issue is that because outside of the classical reportoire there are so few good native 5.1 mixed recordings available, many people in the audio crowd would understandable opt for the 2 channel upgrade anyway. However, this is not because a 2 channel 30K system is better than a 30K 2 channel system. It is because there is no content to enjoy the superior 5.1 system. Obviously for the movie crowd the equation is different.
So in my opinion you cannot discuss the relative merits of 2.0 and 5.1 without considering availability of content. Interestingly, the way audio is evolving it looks like legacy MCH high rez (i.e. SACD and DVD-A) is dead, future MCH high rez (i.e. Blu Ray music) is not really going anywhere, and 2 channel high rez may well have a future through 96/24 and 192/24 downloads. I personally love MCH high rez audio and this state of affairs frustrates me no end, but what can you do other than spinning your favorite MCH recordings over and over again....
Think of it like this. You have say 20K invested in a good 2 channels system, and have 10K more to spend. Your options are upgrading your 20K 2 channels system to a 30K 2 channels system, or spend 10K on a center channel, pair of surrounds, 3 channel poweramp and active sub. Your 2.0 channel upgrade is deep into diminishing returns territory, while your 2.0 to 5.1 upgrade is a huge net system improvement. The issue is that because outside of the classical reportoire there are so few good native 5.1 mixed recordings available, many people in the audio crowd would understandable opt for the 2 channel upgrade anyway. However, this is not because a 2 channel 30K system is better than a 30K 2 channel system. It is because there is no content to enjoy the superior 5.1 system. Obviously for the movie crowd the equation is different.
So in my opinion you cannot discuss the relative merits of 2.0 and 5.1 without considering availability of content. Interestingly, the way audio is evolving it looks like legacy MCH high rez (i.e. SACD and DVD-A) is dead, future MCH high rez (i.e. Blu Ray music) is not really going anywhere, and 2 channel high rez may well have a future through 96/24 and 192/24 downloads. I personally love MCH high rez audio and this state of affairs frustrates me no end, but what can you do other than spinning your favorite MCH recordings over and over again....