That's just someone's opinion. Not everyone shares that opinion. Some are ok with it. I find it to lack low frequencies to a point that I shouldn't have to be missing anything at this price point. Just my opinion. Very best,
The `Z and a Q701 will definitely give you a nice reference level experience. Not the bassiest headphone around, fairly neutral there, a bit shy for some. But the sound stage and overall presentation is fantastic. Great for gaming. And great for a lot of the genres you described (unless you like the bassier versions of those genres more). You don't need a new dac/amp or anything unless you just feel like throwing money away frankly. I would stick with this for a...
You probably got an open box or refurb model. And payed near "new" price for it.
You don't need to burn in anything. Waste of time. Does nothing. Look for measurable proof. Doesn't exist. End of story there. Rest your nerves.
Put on the headphones, listen to them. If you like everything you hear, then stop thinking and worrying and just lean back and listen to your audio and enjoy.
A Codec/DAC chipset, etc, is all fine and dandy. It can be fine. That's not the issue. Ever. The issue is implementation and how the signal is handled after the chipset converts the 0's and 1's to an analog sine wave. Your bottleneck and sore spot in the motherboard is not the chipset, but rather, the stage where it implements the analog interface and output. That's where the quality drops off the chart. You absolutely would do better with a discreet DAC/AMP that...
Your bottleneck is two fold:
1) quality of media.
2) quality of device that renders media (the headphone).
You do not need an amp. Amps don't just make things better magically. The headphone needs to need an amp for it to be worth while. If you put an amp on something that doesn't need an amp, you get noise floor and it gets hissy and noisy. It's amplifying everything. Efficient headphones don't need amps. So don't read into everything thinking you need...
What are you going to be plugging this into?
I would probably start looking into:
Beyer DT990 PRO 250ohm
Philips Fidelio X1
The HE-400 is on sale for $300 new at Head-Direct this week. Incredible deal, if you can take your budget there. This would be my absolute recommendation at this price.
Ultrasone PRO 750
AudioTechnica A900X (and with the extra money, get some Alpha Pads from Mr Speakers to swap)
Beyer DT770 PRO (80 or 250ohm, doesn't matter)
AKG K167 or K267
Maybe hold out and hunt for a used or deal on a Shure SRH1540?
Options from Amazon:
I would pounce on that UE6000 now. Outstanding price new. Half what it used to be. Otherwise, the A900X if you can. Otherwise, the HM5/XPT100 (same headphone, clones).