Sometimes they aren’t, bought quite a few things from Linsoul that should of been taxed and weren’t. I’m guessing you are in the UK from the £ amount, me too. If I do get hit this time that’s just how the cookie crumbles.
I think you’re right to look away from Sundara and HD650 for your genres. I effectively own both headphones, lovely - but their strengths are aligned to other things.
Maybe could also look to Zeus.
Should really ask first — what are you used to? What are you coming from?
What do you listen to your music through as well, what is your source material?
I’ve got some hd598’s witch are lovely but not really what im looking for. kinda feel a bit lacking, otherwise im mostly using speakers theses days, got some warfadale 10.1s.
listening wise m normally using wither spotify or foobar usb’d to my dad/amp combo.
ive seen the zeus but im not completely sold.
im guessing the hd660s are gunna be similar if a bit clearer and sassy then the 650s?
The benefit to the 660s would at least be an easier to power impedance.
However, I would worry that all of the HD6__ series might provide less low-frequency output than the 598’s you have. The treble smoothness would likely be an upgrade for you. I’ve enjoyed my 58x as a “hip hop can” in the past, as there is warmth and sufficient extension for me - and they still have that lyrical mid-forward presentation.
A good question to always ask, is “what would I change?” about existing gear.