Up mix stero sound

[tim-m89]

Hi, what's available for upmixing stereo sound dynamically (while playing). My main purpose of this is to continue using my subwoofer connected to the black connector of my PC rather than a splitter connected to the green connector.

I use freebsd FreeBSD 9, audacious to play music and snd_hda as my driver. OSS is too buggy for me.

Thanks