Thanks everyone for all these awesome suggestions!!
As I'm trying to upgrade over my HD-598, which I quite like, It's probably going to take a headphone north of the $200 mark to accomplish that. I'm currently listening to the HD-560s and really enjoying them. I think they fit the criteria of this thread rather well, and would recommend them to anyone looking for something in their price range. I may as well copy my thoughts so far from the 560s thread:
"Super close to the 598, as expected. A bit more treble at a certain frequency, and less so across entire treble range. It's something that sounds like it was needed, IMO. Never what I'd call sibilant or harsh, though. The midrange still sounds a bit more natural on the 598, but it's not huge. The bass is a decent improvement over the 598, and nearly as noticeable. Better extension for sure, but suffers the same issue of the 598 that it won't take much boost at all in the subbass before distortion becomes audible.
The 598 still sound
damn good. I'm quite surprised that a headphone that's truly 10 years old (Aug 2010) is even able to hang with some recently released darlings. The narrative sometime seems to be that every 6 months, a headphone comes out that's a significant improvement on what came before it, which may lead one to believe that old headphones aren't nearly as good as what available now. So for anyone out there with old but good cans who may read this and has a serious case of FOMO, just relax, lol.
That said, I'm quite enjoying the 560s. They will be staying for the meantime, and the Phoenix are being returned. I just don't see the hype. Bass was a bit better than my 598 (but not nearly as much as I'd been lead to believe) but the tiny earcups/pads (these are on-ear headphones, I don't care what Sivga says) means my glasses break the seal, and I lose bass. Additionally, the sound was muddy and congested, the soundstage was poor, they sounded shouty compared to the others, and the frequency response was very notchy and uneven. Great build quality and accessories, though.
Oof, just got chills listening on the 560s to Sofia by Clairo, when the wide voices come in at 2:30. So good.
So I'm just gonna keep listening to these (LOTR soundtracks currently) and see if they improve any. They're really good, but I'm not totally sure yet if the slight bump in quality is really worth $200. It probably is, but being that one of my uses is music production, I'm not sure how much sense it makes to have an only slightly different variation of what I already have. It may make more sense to have something that gives me a sonic snapshot from a different angle, although one that is also near linear.
Hmm, listening to Lost in Emyn Mull from The Two Towers soundtrack, there's a particularly stressful passage starting at 3:20 till the crescendo at 3:40 where the 560s seem to struggle with distortion in the bass/subbass region, even with the EQ off at a moderate volume. It seems to poke it's head up at times in other songs as well. For anyone curious, I'm using a Focusrite 18i8 ( a digital audio interface that goes for about $400) to drive all headphones. It makes it really nice for comparisons as there two identical headphone outs with their own volume knobs, so I can easily match volume and compare sound signatures as quickly as I can put them on my head."
@Kammerat Rebekka I like the Flow RT suggestion but found it hard to find reviews on that particular model, do you have any idea when the retune happened? I also like the Ollo S4x suggestion, it's one I looked at before, but I'm not sure I want to go through international shipping returns. It's also cheaper on EU Amazon than what I can get it from the manufacturer for.
@cycloverid that's one of the more interesting suggestions here, and I've heard so many good things about the Sundara in general that I took the plunge and ordered a pair! The fact that they're available on Amazon with their painless return policy is a major plus as well. I've heard about the rolled off subbass which kept me away, but apparently that was improved at some point. If they take EQ as good as you say, I may end up sending back the HD-560s. They'll be here Saturday.