No. I'm using headphones. The game's audio is almost inaudible unless I set the system speaker setup to 5.1 and then have the Xonar mix it down to headphones. It's been this way since the game's release, and the 1.2 patch didn't fix it.
ok, headphones plugged into what. SPDIF output? your receiver's "headphone" jack? See, I'm not sure you're doing the best thing by telling your computer you have 5.1 then at the end the audio will come out of just two speakers. You should be blaming the component doing the downmixing of 5.1... try it, just humor me, tell windows you have headphones. now listen to things.
Do what I did, if you like headphone gaming. buy real multi-speaker headphones, mine hookup to the optical/spdif output (so digital and 5.1 stream) and then the headphone speakers actually have multiple speakers so there really is a benefit at the channel separation...