Hi Pauly,
Although I love the sound of the MIDAS preamps on the X32, I completely understand the desire to use outboard preamps to expand your palette (especially if you already have some nice pres in your collection!) If you want to use a few mic preamps without using a whole block of 8 channels, I would use the "Out 1-8" or "Out 9-16" setting for the X32 card outputs rather than the "Aux 1-6 / Mon" setting. From here, you can go to the analog out page of the ROUTING menu and individually assign whatever direct out signals you want to the outputs. For example, Outs 1-2 could be "Dir Out Aux 1" and "Dir Out Aux 2" while Outs 3-8 could be direct outs from any X32 preamps. You will also notice by doing it this way you will also have the ability to choose a tap point (Pre/Post Fader, Pre/Post EQ). Hope it helps!
Best,
John DiNicola
Senior Specialist, Product Support
MUSIC Group
BEHRINGER