Q. How can I create a better stereo image?

I’ve recorded a couple of songs with just three tracks: acoustic guitar, bass and lead vocal. I’ll obviously pan both bass and lead vocals in the centre. I’ll probably have to centre the acoustic guitar too, since if I pan it a little to one side there’d be nothing on the other side to balance it volume-wise. There wouldn’t then be much of a stereo image, so I figured that a stereo reverb might give the song a sense of space. If I use something like a Lexicon MPX550, how would I route the effect? Obviously, the vocal is mono and sits on one track. The effect return part is easy: effect return to 1 and 2 and pan them hard right and left. But what about the effect send? The Lexicon has ‘R’ and ‘L’ inputs, so would I use two effect sends for the vocal, panned right and left?