Hi @Cyan69, @generic offered a path forward when you first asked this question earlier, suggesting a Focal Clear, leaving $500 of your $2000 budget for headphone and DAC. I’ve just gone through this process myself, and similar to you, I’d spent most of my money on AV equipment over the last decade before returning to audio this year.
I would recommend upgrading the Denon first because as @generic pointed out, that was designed to be a really good surround sound amp, not a headphone amp. Then spend some time with your new amp/DAC to get a feel for the sound with your current headphones, which are all good. That way you’re not replacing everything at once, which will make it difficult to know what to do if you don’t like the sound. Spend at least a week, to let the system and your brain settle in, and if you don’t like it, come back to the forum and explain what you dislike, because that will help all the experts give you an alternative path.
I’d suggest trying out a Schiit stack first, if only because they have a 15 day return policy, so it would be a good way of getting a baseline for what you like or dislike. Also, a lot of people on this forum have either owned or still own Schiit equipment and can explain to you how other amps might sound in relation. I think @lost33 may have one of every Schiit amp!
If you want to keep to the $500 AMP/DAC budget, and you want some tube experience, then the Schiit Vali 2 amp and Modi Multibit DAC comes under that amount. If you want to spend about double that budget, you can get the Lyr 3 amp and Bifrost 2 DAC, which is what I ended up with. From what I have read, it isn’t worth getting the internal DAC option with the Lyr3.
Both the Vali 2 and Lyr 3 are hybrid tube amps, so you won’t get as much “tubiness” as you would with a pure tube amp, but for a newcomer like me, I liked the fact that it only needs one tube, and I can have a little fun trying out new tubes to see if I can tell the difference. It’s been a fun enough experience that I think my next purchase will be a “real” tube amp, but I will probably need to increase my budget for my next amp because I like the Lyr 3 a lot, and I want to make sure I get a true upgrade.
Once you’re settled on the amp, then try some headphones. @generic suggested the Focal Clear. Given the types of music that you like (metal, rock, pop), others on the forum may suggest the ZMF Aeolus, which is a similar price, and is supposed to excel with rock music. Both Focal and ZMF have a lot of support in this forum, and many people own headphones from both manufacturers, so you’ll find a lot of useful information within the forum using the search function.
I hope that helps. I’m not an expert, but I’m trying to explain the path I took, with the help of everyone on this forum. The main thing is that no-one can tell you exactly what to buy, because they don’t know what you like or dislike, so part of the fun of this hobby is trying something out and keeping it if you like it or moving on if you don’t. And even if you like it, you’ll have this urge to find out if there’s something out there that’s even better…