I'm glad you're willing to go and audition the HifiMans. I would also recommend them. I considered myself a Focal guy until I tried the HE1K V2's and I was instantly converted. Liked them so much I made the considerable leap to the Susvara, which was another huge improvement. I hate to use such an overused term but these truly are "end-game" for me (and I got a pretty substantial discount off the $6K list price). They have so little clamping force that if you tilt your head forward or back they will fall off! HFM obviously placed a major importance on comfort.
I've had a few Audeze models and they're all just ridiculously heavy. Focals are much better. I've never heard the Utopia 2022 but it's the only other HP I would still like to. The Clear Mg is an excellent HP and in your price range. A little more clamping force than the Susvaras but I suspect that will be true for pretty much any other 'phones.
I use the McIntosh tube headphone amp. There's a review you can easily find if you Google it saying that, with a tube change (which I've made), it is the best HP amp the reviewer has ever heard (this is from an older, very seasoned reviewer) and I believe it's a fair bit less expensive than the balanced Woo Audio choices. Only caveat would be that I would try to have a DAC or preamp with a volume control because the one on the Mac is annoyingly hair-trigger. With that taken out of the equation it's pure bliss.
Definitely stay with open-backs. The best closed-backs I've personally heard are the Denon 9200's ($1600 and extremely well-made). I use them nightly so as not to disturb my wife and they are quite good but can't hold a candle to the Susvaras.
Sorry for such a long-winded response but headphone rigs are something I'm (obviously) pretty passionate about.