I had the exact same question actually, lucky I saw this before posting as I didn't want to double post.
My maths is bad and it seems like calculation city any time I google to try and figure all this ohm and power matching stuff out. I just want to know what headphones I can use and still get enough volume out of them to mix, seems easier said than done.
Maybe this will help...
It looks to me from reading this that most USB powered audio interfaces (mine is a USB 96 box also) won't actually be able to power a lot of higher impedence headphones properly, and you may not be able to achieve the volume you need. That's at least what I could take away from reading through that there. It does say "high volume" though so you may need to do some research on the headphone sensitivity etc and then do some calculations from there.
I'm interested to know if anyone here has anything else to add.