I'm a little late, but the K601 has more mid-bass than the K702 and is much warmer than the K702 and has smoother treble.
The K601 is a lot better for rock music than the K702 for sure, but I don't listen to much of that. Stuff like Primus and Pearl Jam sounds good on the K601. Even Radiohead.
The Q701 is definitely warmer than the K601 though, but there still seems to be more mid-bass on the K601, but less treble. It's kind of hard to describe and this probably makes no sense.
The K601's mids seem more neutral than those of the Q701.
My guess is that the K612Pro will be as warm as that of an HD-600 maybe.
I no longer have a K601 since I swapped it for a K400.
It's really confusing how bassy and warm the K400 can get with those 65th pads. I'm loving it right now..
EDIT: BTW I hope they don't phase out the Q701 or the stock K702 pads. I still think the Q701 sounds better than the 65th anniversary. Not everyone will and it depends on preferences.