Got my K7XX's. I like them better than the K712 right off the bat. Better more textured mid range and a smoother treble. None of that dryness the K712,K701,K702 suffered from. right away I'm familiar with the sound. It's in Annie territory which is absolutely fantastic, I'm over the moon about that as they didn't cost me an arm and a leg. Bass is extended and around neutral, it's present, in line and great. Vocals sound natural and not as pushed back as the other AKG's, quite upfront but not too personal. Soundstage is smaller than the K712.
It's a warm headphone but not overly so, I would say around the HD600 in warmth but not as warm as the HD650. HD650 has a smaller soundstage, slightly more intimate in the vocals. I like the K7XX better as it wins in more areas. Bargain for those who got them for cheap, seriously these will compete with anything. They compete well with my HE400i. Not tried them for gaming yet to get a better impression of it's image.
Listening will go on for a while and I'll write a more detailed review on them. Reason for the impressions so early is because I'm so used to all the K7 series.
Edit
After more test I can confirm this headphone is the newer Annie. I don't have the K712 with me at hand but sonically I know their sound so well and they still have the differences I mentioned. The K7XX ear pads I have seem to be the K712 ones after actually taking time to look at them.
While gaming using the Mixamp pro > Vali > Xbone/PS4 the soundstage is a more closed one. It's deep but doesn't have the air and space of the K501, K701, Q701 and K712 . The K7XX sounds thick just like the Annie. For gaming it's inbetween the K601 and K712 in terms of staging which is still top notch. Don't expect it to be the K701 because it's warmer and lusher sounding.
Positional Accuracy is on par with the other AKG's. The mid peak like the Q701 only shows it's self when the recording is like that. Mellow music sounds mellow while aggressive music will show the minor peak. Again this is minor, it's not K712 bad and most people won't even notice it but I am sensitive to that region and trust me, it isn't bad unless you are worse than me! The old Annie had it which is this headphone.