If you are having problems finding a suitable tv with variable audio output, one option is to use a programmable universal remote that will control the tv and program the volume buttons to control the sound system instead. I use a MX-500 remote bought for around $100. It controls everything, Tivo, sound system/DVD player, the plasma screen, and the cheap DVD recorder I bought to act as the tuner when using cable or the antenna. It replaced the VCR in my system.
A side benefit is that you can program the buttons so that the same button is the fast forward for the DVD player, the Tivo, and the VCR if you have one. That makes it real easy to use. In addition I have the same remote at home, so it is almost idiot proof.
That should expand the list of suitable TV's.
'04 Alpine Coach 36' MDDS