Hi Darren,
I'm sure others will answer your question more clearly. I use a emu 0404 interface and press the mono button to hear my vocal in both headphones L and R while I'm recording. Once the track is recorded even tho it's a mono track it sits nicely in the center of a stereo mix. I don't actually record any vocals in true stereo. I suppose you could but you would need two mics or you would have to run through a mixer and assign the one mic input to two channels panned left and right.

Sundance