On the Xonar D1 I have here, I can enable a thing called "Dolby Headphone" on Windows (no idea whether that's a DSP thing or just pure software.) And it actually works; when I first tried it, I was expecting some crappy proccessing done to get some form of cheap "surround" illusion, like that "Creative CMSS-3D" thing that never worked. But in fact I was surpised to be able to hear sounds coming from several directions even though the headphones are plain stereo.

I don't think we'll ever see that on Linux?