A lot of them do have this, it's usually call stereo-4 or something along that line. My Sunfire prepro has party-4 and party-5 mode.
on my Denon 2803 when I put it in 5 channel stereo mode the dialogue started coming out of the rears and it sounded great and very intimate. In Lord of Rings I could hear Liv Tyler whispering my ear and I was completely involved in the scene....BUT...the 5 channel mode also killed the great surround feel of the crowd scenes and big moments. The cinema II mode for movies handles these well and is the 'traditinal' expectation of the home theatre....but limits the dialogue to the center channel....so I'd like the best of both and get the big surround feel with the intimacy of having voices nearby.
It just feels like 'center' should be where I am..not pushing out from the TV for a truly involved experience.