Having had the K7XX (modded), and now the HD650, I'd pick the 650. The XX are strikingly similar to the K712 from what I've read. The AKG is great for soundstage, but the detail and "live" feeling to music and anything with vocals is the major selling point.

Keep finding myself looking at these.
If you ever do, make sure you get a post November 2015 unit..you are getting a good headphone if you do!
How do they compare to the HD650 ?
Sounds like the HD650 is something I should look at in the future but I'm really looking forward to using the 712 in gaming.
Are the highs as harsh at the DT990? I really liked everything in that headphone but the harsh highs
I find the X2 the complete opposite, more V shaped with a sparkly treble but not very detailed..although the way Philips are, I wouldn't be surprised if there's some floating around with a rolled off treble! I'd actually like them better if they rolled off the treble and smoothed out that peak!