I posted the same question in several places last year and got no cost effective solution, and finally had to find one myself.
No offence to the person who posted a long listed of items to buy including a besound core and then connect it to headphone out of TV....that for me is total waste.....
The problem I had was volume control in a preamplifier. The cheapest solution is Cambridge Audio C500 preamplifier. It accepts 4-5 inputs of sound source and has 2 parallel outputs in stereo.
I used this to connect my Beolan 7.2 as soundbar for normal use and Beolab 8000 for Stereo Music. Output goes to both set of speakers always and we can power on whichever we need. I get Volume control as well as Bass and Treble control through C500. C500 comes with remote.
All you need to get is a power trigger cable set from Steve from Soundheavenly, for connecting Beolab 9 to C500.
As for TV, I have a samsung 55 curve. that comes with a line out mode, which in itself doesnt have volume control, which is fine as c500 can take care of it. This is by far the cheapest solution without losing sound quality. Happy for someone to prove me wrong.
cheers
Ramesh