I don't think you need to worry about harming the amp or the headphones by using low impendance headphones.
I actually have the Momentum 2 On Ear Wireless, so not the same, but similar-ish.
They have similar, if not identical active/passive impendance ratings.
I tried them out when I got the Crack, can't remember what they sounded like, but I prefered the sound of my 80 Ohm Beyerdynamic DT770.
After upgrading my Crack with the Speedball however, the 80 ohm Beyers stopped playing nice with the Crack, I found.
Luckily by then I had a HD6XX.