There is a very nice little program called Center Cut GUI that allows one to produce either an isolated center from a stereo file or else to remove the center information while retaining the stereo sides. This is usually accomplished by FFT, I think, in Adobe Audition's Center Channel Extractor, which allow for much more manipulation of the effect but can produce some very nasty artifacting with the majority of the settings. This little program uses FHT and allows for a single setting, which from my tests produces a very clean sounding result.
I would respectfully request that you take a look at the free source code and see if it's something you could add to your program. Here is the link to the souce code:http://www.moitah.net/download/latest/Center_Cut_GUI-Source.zip
And also to the topic on VirtualDub forum:http://forums.virtualdub.org/index.php?s=93a59cd5c98ed917daddc036e615adc6&act=ST&f=21&t=12627&hl=
For an additional topic on HydrogenAudio forum on a winamp plugin:http://www.hydrogenaudio.org/forums/index.php?showtopic=17450&
The program was cowritten by Avery Lee and Moitah and is free.
Thanks for your consideration,