Hi,
my ears grew tired of listening to playing just from the headphones and EQing my sounds just based on them was found to be.. hard, so I bought myself a pair of micro monitors (IK iLoud Micro Monitors). Setup was easy, using stereo outputs from Monitor / DI out.
The weird part is that when I'm trying to set the aux routing levels Aux In -> Main levels seem to be uniform with Aux In -> Headphones. I have them both at 4.0 and from recordings I've made from main compared to what I hear in the headphones things seem to be fine.
However when I use the monitors instead of 4.0 I need to set aux in -> monitor to 1.3 to get a similiar (not exactly the same, but close) mix between guitar rig and aux.
Is this normal? Am I doing something wrong? Have my headphones and main mixes been just on chance the same? What's going on here 
Fortunately the output levels to outside devices seem to only affect the main output volumes, no the mix so theoretically when I find the correct mix for every device they same the same regardless of what main levels I set them..