Short version: I recommend you try out a pair of Sundaras or Audeze Penrose.
I play Overwatch competitively (not well, but I try).
Below are my notes from the various headphones I've tried (and currently own).
The only dynamic drivers that let me clearly hear all of the sound cues in the middle of team fights is the HD800s. They are fine for gaming without EQ (being bass light actually makes it easier to hear footsteps), but sound fantastic with EQ. I use the Dekoni Hybrid pads for them for added comfort (and EQ the changes to FR) from larger contact area and slightly increased clamping force (stock will fly off your head if you move around). If you are looking at headphones for over $1000 for gaming, this is what I'd recommend.
Focal Clear MG sound fine, but I like them better for music. The increased bass over the 800s makes it a bit harder to hear sound cues. Decent alternative to the HD800S (it's sometimes cheaper). But you have to be careful to not boost the bass or you might get clipping and damage the drivers (I returned two Focal Elexes because the drivers failed).
HD6XX, DT800 600 Ohm sound fine until you're in a team fight where the sounds just get smeared together. KPH30i is hot garbage for gaming. Razer Kraken Tournament Edition are fine for gaming, but the 3D effect is garbage, mic is bad, and sound cues get lost. I gave away my X2HR because it also couldn't handle team fights well.
Corsair Virtuosso SE. Good battery life (20 hours IIRC), good wireless range (half my house) good mic, ok drivers, worst tuning I've ever head in a headphone (correctable with EQ in the iCue app). People do use these for the highest level of gaming so they work. But you won't hear footsteps in the middle of a team fight.
Audeze Penrose. Ok battery life (15 hours), bad wireless range (works in the room with my PC and the room next to it, but not further), passable mic (people will understand you, but the sound is compressed & tinny), requires a substandard app to change EQ (and that only allows 1 db adjustments, not .1db, can only tell you battery % / make changes when connected via USB, etc.). Drivers are fantastic and you get excellent imaging. They are about the same price new as open box Sundaras and I think roughly comparable in performance. These are great for queuing for a match and then doing a quick house chore, go to the bathroom, etc. I never tried the Mobius because I haven't found fake surround sound (worse for imaging vs in-game Dolby Atmos) and head tracking headphones (this is cool in VR, but VR headsets have head tracking already) to be useful in competitive gaming. They have their flaws, but they sound great and compared to other sets I've tried are "reasonably priced."
I get almost the same performance out of my Sundara as I do from HD800s (and being $1000 cheaper than HD800s makes them my recommendation to you). Aryas perform even better, but not $1300 better. You can get open box Sundaras from Hifiman's store at a decent discount but WITH the full warranty (how I got mine). I don't use Sundara because I own and use the HD800s. I would recommend the Sundara for gaming (but they aren't as good with imaging as the Penrose).
Argon MK3 are awesome for music, movies, and casual gaming. But they are WAY to bass heavy for competitive gaming. Protein pads are key here, otherwise you won't get good directional sound queues (I tried lambskin pads at first, they sound nice, but I couldn't hear flanking enemies). I recommend these, but not for comp.
Sivga P-II (basically a slightly differently tuned Sendy Aiva) probably would work, but they are more expensive than Sundaras, weigh more, require more EQ, and I don't think the driver is as good as the Sundara. They look really nice, but other than that not a great value.
Koss 95X are pretty great AND pretty terrible. After I got them, I could make shots just from sound cues (before I had to pan to the general area I thought the sound came from and then flick to shoot). Even with everything in game exploding all around me, I could hear flankers foot steps. BUT, mine built up an electrostatic whine that was pretty maddening (I'd have to power it down, disconnect the 95X from the energizer, and discharge each pin with a metal probe multiple times a day). They also sounded a little muddy (not sure why, but the sound while accurate never sounded precise). I replaced the energizer with a Stax 353X and thought it was a little better, but not much (and the whine was still a problem). I think the Audeze Penrose headset is better frankly.
Stax L700 Mk2 on a 353X energerzer provided the clearest sound for comp, but outrageously overkill / not at all cost-effective. I got the L700 because I already had a 353X (95X is a gateway drug) it totally solved the whine and muddy sound. Blue Tac mod (improves seal so there's actually sub bass in the FR) and EQ and this is hands down my favorite headphone, but I would never recommend anyone buy it for gaming (well, to be completely honest, it's not substantively better for music either). It's the most expensive headphone I own, has the worst build quality, and makes me look completely ridiculous. The headphone + energizer will set you back ~$2500.
Can't help you on the amp front. I haven't used the Asgard 3.
