I actually upgraded from HD595 to Q701, and I love it. Their signature share some similarities: neither of these headphone have very boomy base, they both have a bright sound and wide stage. If HD595 have served you well, I think Q701 will simple do a better job. To me the Q701s sound superior just about all around. But ...
While the HD595 isn't too picky on the amp and source, the Q701 is quite different. I started with ipod 6 gen -> Fiio E12, far from the best in amp+dac department, but they work the H595 beautifully. Not so much for the Q701 though. The Q701 still sound good, but flawed, like I normally read others complain about: highs are too bright and lack of control, mids are a bit dry, lows are a bit weak and muddy.. etc.
I suspect E12 couldn't bring out Q701's full potential. So I tried M-stage. This time the Q701 sound amazing, those flaws I mention are gone. And if I use a better source they sound even better, but not as much as the M-stage's improvement IMO.
So from my experience you might wanna invest more in the amp, it will serve you well.
I do enjoy the Q701 with Trance, they sound very fast with nice clarity. I like to listen to infested mushroom with them. For classic rock, I think they are great in general, but sometimes the bright highs bother me a little, I guess that's fatigue in headphone terms. For games they are excellent. I love the sound stage and detail.