Nick, this is such a hit and miss procedure..

You don't want to spend more than $1,000 for software...do you?

The audio files need to be as centered as possible for the vocal track, too far to the right or left will reduce too much content from the file...
Also effects on the vocals are usually stereo and pan wide left to wide right, making it impossible to remove from the audio file..

The higher price software allows you to set the frequencies that need to be reduced, and also the location of the stereo field....but if it falls as I described above...it just doesn't work...Save your money..