And god no, bass boosting the DT990 would murder the sound quality. The Q701 loves a good bass boost BECAUSE it's not that bassy to begin with.
I wonder how the 32ohm's graph would look like. I guarantee it'd probably have a bigger bass hump, and less treble peak. It's pretty bassy, so I'm thinking you probably wouldn't like it. It has a lovely impact, but even for me, it's borderline too much. That's probably why the 600ohm gets the most love. It's clearer, less bassy, but I still say the treble is hottest.
Yes, Beats Audio... it was the only option available.