Good answers so far in response to your post, but I have a couple of questions:
- Why do you care about the impedance of your headphones?
From what I understand, the high impedance design is suitable to pro installations where multiple headphones may be in use in a control room. With longer runs, higher impedance and lower current are advantageous, but none of this matters for a consumer / at-home situation.
- Why the preference for solid-state vs tubes?
Here, I'm just curious. I prefer solid-state too because it tends to be lower maintenance and a bit less fussy, but there's some really nice sounding tube gear out there that may be worth exploring.
For the first one, I don't, it's not an indicator of sound quality.
For the second, and more interesting for me to talk about. Simply speaking, it's a superior way of doing amplification. If you define amplification as what it formally is - take signal A, amplify it without messing with it - just give me more A.
Imagine you had a camera. Taking nice clean pictures. But you want to zoom in on a scene. You add lenses and zoom in. Do you want the same clean image - or do you want some noise and trash added to the scene when you use the lenses - e.g. the lens has a bunch of scratches on it?
Seems pretty clear that you would not like a scratchy lens - why is it so difficult for people to understand I don't want a noisy, distorted signal and that solid state is a better way of going about it. Not saying you can't get clean amplification with tubes - but SS is easier to do well, cheaper to do well, and the products are more reliable in general.
Now, liking certain types of distortion is all well and fine. Individual differences are real, even if we can agree on an average target - there's enough individual flavor there for people to tune things to their preferences.
Nowadays, I see no reason to add that flavor by hardwiring it in the chain via poorly measuring gear. If I have a clean, transparent foundation, I can tune it how I want (well, my preference is to get the cleanest possible signal to the headphones so doesn't apply to me really but in general it does).
It's quite a simple argument.
Further, I find subjectivists are walking into a wall of contradictions when arguing that amps and dacs should indeed sound different - and then saying "trust your ears" or "it may sound better to you". Well, that means that any subjectivist review is completely invalid - and non-informative - if my ears are the only judge of whether something is good - then your ears are unimportant. Now add to that the fact that audiophile terms are used inconsistently even between reviews of the same reviewer - let alone between reviewers (I'm actually working on designing a study to check consistency of use across popular reviewers for the same products and across products to quantify this inconsistency).
Here's an example, Zeos loves class A amps because they're "warm, and wide and lush and shit rainbows" - when he was reviewing the FA-10 after reviewing the FA-12 from Flux Labs - he failed to see in the documentation that it was also a class A amp just like the FA-12. When talking about the FA-10 he was convinced it was not class A - he still liked it for the power you get and for it being clean etc. but only if it was class A it would have it all... Well, it is class A and he can't tell the fucking difference without knowing in advance - or in this case - he inferred a difference where there was none.
Of course, fit, looks, feel, and sound characteristics will influence whether you specifically like something - an objective measurement won't tell you for sure that you'll be happy. However, if something measures as clean in terms of noise and distortion and you can see the frequency response - and you have enough experience to know what your personal target is - you can make informed decisions what to demo (or buy outright if you can't demo).