I would skip Q701... I've compared HD800 side by side with Q701 and Q701 are lacking in several things:
1) They have less subbass and overall slightly lack fullness in comparison to HD800 (less realistic symphonics, bass drum etc.)
2) Vocals do have some strange tone and lack a bit of depth... I've definitely heard that 2khz emphasis and it bothered me a lot (Q701 were tonally off)
3) The treble of Q701 sounds a little bit plastic, electric guitars do not sound natural as well as symphonic passages...
4) Soundstage of Q701 is very nice in width, though they lack especially depth in comparison to HD800... While soundstage of Q701 is rather left - center - right with nothing in between, HD800 are more semicircular - so better defined soundstage, more compact.
5) Imaging of Q701 is not quite on the level of HD800... I agree they are rather fuzzy.
6) Comfort is nice but definitely not on the level of HD800... HD800 beat even DT880 for me, by quite a margin. That said, I find Q701 more compact and better for daily usage in busy environment (like in studio).
On the other hand, I must hear K712 pro as I believe they could possibly correct Q701's biggest flaws and therefore be really balanced and versatile phones. I do not expect them to be directly on the level of HD800 but if they are less tonally off than Q701, I will be very satisfied.
Btw, are HD800 worth 1500USD? Definitely not if you dont know exactly why you are paying so much for them... If you want perfection, if are seeking the best imaging, soundstage, comfort, hyperdetail and very neutral FR, then yes. But if you are willing to live with a headphone that do most things right but lack in certain aspect or aspects, then my answer is - definitely do not buy anything more expensive than 500USD. Go and listen to several similarly priced headphones and decide for yourself. I would suggest Q701, K712 Pro, DT880, HD600 and HE-400...