120 mg of codeine is about equivalent to 20 mg of hydrocodone (13.33mg of oxycodone). If you are wanting to take more codeine, I would proceed cautiously and only dose 30 or 60 mg of it. I would not add any more benzos to that mix as you're already at an equivalent of 9mg of Xanax. If you do decide to dose more benzos, wait until the codeine has kicked in and assess your high before proceeding. I'm not condoning doing these things, I'm just trying to outline the best possible way you could go about dosing more in case you decide to do it. Like I said though, I do not recommend this.