Kal
With blu ray specifically I have not found this to be true, in movies it may have a slight effect on dialog, however 100% of the blu ray "Concert DVDS" specifically I don't have a single one that does not come with a 2 channel downmix in the menu..
Acutually from my experience so far with my setup which in the past was not true of standard DVD blu ray 2 channel even thru the digital outs does not vary at all from the multi-track option. Why? Not sure accept that in the new technlogy and format of making the blu ray discs they have seemed to somehow auto-sense regardless and your front 2 main channels are going to always be mixed with full range frequency.
Again this is not true with DVD, for example I can take your new Harry potter Blu ray or whatever which has Zero audio options but true HD surround or whatever and put it on with NO subwoofers, No center channel, and just running on the mains I still get as good or better explosion impact, and dialog with less channels and equal to running it thru HDMI to a multi channel processor! Since these revelations and the importance to me in specific of do I care as much about Transformers making it as accurate sound as possible like a mountain coming down in my house? I have decided movies are not that critical and the concert DVD's and music is far more necessary to get the attention and money.
Again this was never the case with Standard DVD, and definitely a KILLER with concert DVD's that if you were running the concert in 5.1 or 7.1 it sounded very hollow or totally aenimic in power output compared to using the 2 channel mix.
I am sure depending on the source, the processor, etc... This will all vary system to system to some degree. Again today digital has advanced far beyond 5 or 10 years ago and is cheaper, less and less issues with audio mixes have been the normal in my case recently with new releases over the past few years.
