how does your computer feed the 6.1 system, through different connections from the soundcard (i.e. stereo front, stereo rear etc) or is it a coax/fibre digital connection?
If you have seperate feeds from the soundcard, you could look into a decent bookshelf speaker and amp combo to replace the fronts of the 6.1 system. therefore having a much better stereo solution, but keeping the 6.1 for games/films etc.