Brett, You can use aux 1&2 out and the 4 sub outs to give you 6 cue channels to feed your headphone amp. They'll all be mono, but this gives you the most channels I can think of, and still allows you the fx sends & returns if you want a little reverb in the cans. Then just assign whichever channels you want to the appropriate aux send or sub assignment. Feed your PC from channel inserts with mono plugs in to the first click on the insert jacks. This is post trim, post Low Cut and pre EQ. The low cut might be handy if you have any boominess on drum tracks you can't elinate by mic placement. Good luck.

Riversedge thanks a bunch!
I am using the first click of the insert currently to run into the Motu828 interface already (guess I should have clearified that). I didn't even think about using the sub outs for headphone mixes!! thanks again. That would give me about 4 different mixes right? Is there away to assign one channel to one sub group or does it have to be one channel to group 1-2? Can I pan hard left or right to get it to go to 1 or 2? Will this effect the signal getting sent to the 828? I would guess not cause because the pan is after the insert correct.
Thanks again

Brett, You're correct, assigning a strip to 1-2 and panning left will give you output to sub 1, panning right to sub 2 (same scenario for subs 3&4). This shouldn't affect level sent to your 828. Don't forget about using aux sends and returns 1&2 to your headphone amp, then you've got six channels.