SRS® TruSurround XT® output plugin
 

TruSurround XT® output plugin similar to Windows Media Player SRS WOW effect.

About SRS® TruSurround XT®:
SRS TruSurround XT® was developed to address this need. It delivers a premium virtual surround sound experience from any multichannel source over just two speakers or headphones, transforming any audio material, including mono, stereo or surround encoded content, into breathtaking virtual surround sound.

very difficult, because SRS wants $$ to do this: SRS Licensing

the Winamp PRO fee is for mp3 encoder license and full speed burning (by Roxio/Sonic Solutions), so another licensed component would rise the cost

in DSP you'll find some freeware similar tools

*crap removed*