Just to add to Beep's excellent comments, if you have any stereo tracks from your Sim, using Channel Tools on it gives you the flexibility to place any part of the signal anywhere you want in the stereo field.
 
It's an awesome tool in this application.

One additional trick is to invert the phasing between a left and right panned tracked. In your left panned track, you'd boost 1k frequency by some amount of db. In your right panned track you'd cut it the 1k frequency by some amount of db. Or just use Panipulator plugin. You get the idea with my Late Arrival song. (Listen through headphones ) at 0.35 the guitar (two panned guitar tracks) sounds like it's in the top half of your headphones, then at 0.41 the additionally tracked (two additional panned guitar tracks these tracks are using Panipulator) guitar sits lower in the headphones.
 

I like panning similar passes, like chords, opposite each other and put riffs and leads nearer to center.
 
If all I have is a lead part I like to set it pan opposite to a synth or other instrument.