load 2 tracks of the song into real band and load the knockout vst into one then re-mix and render all tracks to stereo wav file

you can isolate the center channel with something like

http://blog.wavosaur.com/extract-vocals-from-song-with-kn0ck0ut-vst/

http://www.cloneensemble.com/vt_main.htm

http://www.elevayta.net/product13.htm