Damn it where's 7th gear when you need it?!
Could be there's specific set up feature for when watching different sources, eg only stereo in tv mode but full surround when watching dvd, check the instruction book if there are different set up options you can control.
Remember though, surround sound is only there to provide depth to the sound so the rear speakers wont be active a lot during normal tv programs, only during things like action scenes, of which I doubt there's too many in an episode of Coronation Street!!
As for balance, if the rear speakers are too quiet for your tastes you should be able to adjust the levels of the rear speakers up a bit independantly of the fronts.
Simple answer, go back to the instruction book and look for information on set up adjustments.
A4 3.0 Quattro Sport - Gone & missed everyday!
Current road going missile.....
........Smart Roadster - arguably the most fun you can have in a car without using lube!!