You're going to buy the HD8000s? Damn, I'm impressed. Wish I had the courage (& depth-of-wallet) to make that move. But then I'd have to buy both the HD8000 & the Empyrean...my head would explode & make quite a mess.
Again, I'll try to answer your question, though w/a brief exposure it's difficult.
- The HD8000 is a physically large, handsome, obviously well made headphone in the Final style--black/round earcups, good pads, w/padded metal headband. They felt good on my head, but not a soft/squishy kind of good. The headband padding, for example, is not super deep or ultra-soft. It felt great, but no telling if longer exposure would wear on me.
- Clamp-force was reasonable. Don't even remember it registering much (one definition of "reasonable"). But given the bullet-proof design of this headphone, I'm sure there's steel inside the leather-bound headband, allowing any degree of loosening/tightening you'd want.
- Thought the pads felt quite good, large diameter, approx same size as the AKG 553's I had a couple yrs ago (~110mm), but w/pads a little deeper--and made of some kind of velour, maybe polyester, w/firm but comfortable inside foam. I liked the pads.
- Weight seemed moderate/reasonable (then again, so does my Ori & my friend's Eikon, so maybe I perceive weight differently).
So to summarize, I thought these headphones felt pretty good. No alarm bells went off. And re the headband, if that becomes a problem (hot-spotting, etc), just get yourself the best headband pad around, the ZMF Pilot Pad. For a headphone of this quality & price, if it needs extra padding on the headband (and I mean only IF it does), that's a small price to pay to make it a non-problem.
If I were on the fence about buying the HD8000, comfort wouldn't be the deciding factor/source of doubts. Price, maybe, but not comfort.
As far as the Empyrean goes, the comfort was basically off-the-chart. The earpads are quite large, deeply padded (very comfortable), and that teardrop shape means they conform to the jawbone/back of ear, where it meets the neck, as well as any HP out there. The headband is not just wide, but suspended/levered in a patented way that that it won't hotspot the top of head. I thought the comfort of the Empyrean was just like its midrange--luscious, sink into it like a big hot-tub.
- The design of the grill on outside of each earcup is just beautiful. Sorry, but I had to mention the visual stuff...
Trying not to make this into a beauty contest. These headphones display very different design aesthetics, both physically & sonically. Both approaches have great value, but people react to the physical stuff (if anything) more different than they do to the sonics.