Find for the best SOUNDSTAGE headphones. Massdrop offers to competent ones: the AKG 7XX and the Hifiman 4XX. Many from the audiophile community said that 7XX suits better for gaming since they sound wider and the theory also says that a bigger driver like the plannars also helps with soundstange. Most of the forums said that nothing beats the HD 800s on soundstage...but shit's expensive. My personal recommendation is Beyerdynamic DT-990-Pro 250 ohms version. In my case , since I'm on a budget, I changed the padding of my 6XX for a hybrid one(the bigger, the better) and leather also works but be sure that those are big pads, take the foam for something thinner or with holes but keep the original intact. At last amp and dac matters too, so use balanced cable (since you have a jotunheim) and a good powerful dac (I use a Topping D50 for its customizable sound) since in the case of the 6XX the escalade better with the power.
Note: investigate about EQ configurations for gaming since FPS benefits for focus sound on mids and use the one that suits you.
EDIT: I forget to tell you that tube Amps are also and option. This amps exchange some accuracy on sound for soundstage. My preference is the DarkVoice 336.