I think you underestimate the number of people who would benefit from a dialog channel, and the number of people who are having trouble with TV lip synch.
Soundbars solve these problems, but are poor on music.
I posted earlier in the thread I'd love a 3.1 (or 3.2) system as I'm not bothered about the rear channels now.
Since posting that I've become a bit obsessed with ripping my music concert DVD's and trying to get the best out of them.
Something I didn't realise until very recently, with my AVR (Denon 2311), whilst you do a scan / setup and alter the levels for each channel to taste, I thought it remembered the settings for each input .... i.e. DVD player or HDD recorder. I couldn't understand why some programmes sounded great (after manually adjusting to preference) and others, whilst the surround effects were brilliant, you couldn't hear the dialogue and the rears were overpowering.
I discovered about 4/5 days ago, I thought it saved the settings via input but it doesn't, it saves them according to whether it's 2 channel input (which it fabricates 5.1 surround) ...... OR if it's 5.1 / multichannel input.
I'd watch something that was 2 channel and it'd sound brilliant, then watch a movie or music DVD in 5.1 and you couldn't hear the dialogue.
I've changed the settings to match across the board and dialed back the rears which were way too much both with 5.1 for music and films, they're all now crystal clear.
Having discovered that, I've also started trying the various audio recordings on the music DVD, ie. stereo or 5.1, I can switch the AVR to stereo or direct input and with the DVD's select the stereo audio or 5.1.
Having now fairly extensively tested all the scenarios and have turned the rears down so much it wouldn't make much difference if they were there or not.
Playing the DVD as stereo and letting the AVR decide what goes to the centre / mains and sub .... the sound is absolutely incredible, the centre is the vocalist in the middle of the stage and the rest of the band placed where they should be.
I will just add .... I'm using a HT Bypass setup at the moment and all of my music is played as straight stereo through my integrated without a sub, I think 5.1 or more has gone out of vogue but I still think it's nice to have control of dialogue for films / music DVD's etc. but probabaly not necessary for most stereo music situations.
Just my 2.5 p's worth.