Audio playback: Extend stereo sound to 5.1

Hi,

I was wondering whether it is possible to use e.g. Amarok or VLC to play for example my stereo MP3s and on the fly extent it to 5.1 sound. This question mainly 'inspired' by the capabilities of AC3filter under windows, which offers this and various other nice features. For the playback it self, I am connecting my PC via Displayport / HDMI to an receiver.

Thanks for your help!