need to fatten this guitar tone..

For one, I would ease up on the editing on the guitar tracks. Where are you hi-passing the guitars? Maybe try lowering the cut-off a bit. As for the bass, try to split it into two tracks, HP one, LP the other and limit the LP track so that the low end doesn't move. Or, you could try a multi-band comp and treat the area below 200Hz to steady out the lows.