I have the exact same issue too, it is very disturbing. I have an Asus Xonar D2 if that matters.
I have a Xonar DX and have the same problem, the whole sound has a strange echo, even if I disable every filter in my soundcard, 3d effects, >2 channels, etc.
Tested with headphones with only stereo and everything disabled (Dolby, etc) and it's the same.
