At least some of those in your pic appear to be OTC tube amps... (Output Transformer Coupled). These are still "true" tube amps but are not 'Output Transformer-Less' tube amps. Whether or not any of them are OTL/OTC/Hybrid can only be answered by cracking the case. Personally a cheap tube amp sounds like a good way to fry some cans to me. I would stick to Darkvoice/La Figueroa/Little Dot/Schiit/Bottlehead on the lower end of the cost spectrum. Woo, Rogue, Feliks Audio, Cayin and others on the higher end of that same spectrum.

When the rated wattage drops at lower ohm rating the device is current limited/has a very high output impedance. Either could create issues with the planar, the former being more impactful than the latter.

For me I tend to bucket them into macro and micro. Macro detail is largely dictated by frequency response.

Going from a headphone with a dip in a certain frequency to a headphone with peak in the same frequency may present "new" details. Then when you go back to the old pair you can still hear the "new" detail... because you know what to look for now. The new pair just made it stand out, due to a peak/lack of dip.

The micro/low-level/nuanced details are the bits that I think differ due to things beyond just frequency response/tonality. Here distortion and other factors are at play IMO.

To put it another way, macro is noticing a new background instrument/effect because you either corrected a dip in the fundamental range or used a headphone with a peak in that same range. Hearing additional texture on a guitar string pluck would be an example of a "micro" detail in my book.

Rogue RH-5 is 3.5W into 32, despite having more powerful amps the Rogue is my preferred pairing with the HE6se. A bit overkill unless you are also using it as a preamp but for dual use systems it's been a wonderful addition.

I am fully satisfied barring an audition of the Hifiman Susvara (and a serious dealer discount). The amp/cans in my flair with a Marantz SACD30n and Music Hall MMF 7.3 as sources keeps me quite happy.

That particular amp allows you to take impedance matching a bit further... one of the TRS jacks is 120 ohm output impedance, only really useful with HD800, T1 Gen 1, etc... but can be fun to experiment with.

I was in the process of a quick edit, see above now.

Certain devices may favor one output over the other, it doesn't make the "balanced" headphone output universally "better". Let me use the Cayin iHA-6 and your Sony as an example... via the trs (SE) output they would see a 10 ohm output impedance to a 16 ohm nominal headphone, this is an impedance matching issue. Assuming the Sonys are like most dynamic headphones there will be a rise in impedance near the reasonance frequency of the driver... in the bass region... that gets boosted when fed a high output impedance.

Via either the dual 3 pin XLR or 4 pin XLR that same Cayin has a .3 ohm output impedance which would NOT result in any measurable FR changes. Headphones below 80 ohms are best ran via these "balanced outputs", above that threshold there are minimal differences between the two on that device.

My gut is more on being accentuated by the particular FR vs a driver technology but I haven't put much effort into "unraveling" this one. I don't do much vinyl record listening late at night which is when I tend to choose headphones over speakers. Should I hit one of those sessions I just skip the HE6se/Arya and grab the ones I mentioned.

For whatever reason I find the Elex & HD650 to be more forgiving than my HE6se & Arya with records.

I definitely do this with good quality pressings but anything with a bit of surface noise is quite noticeable on headphones. The pre-amp in my speaker system is also the HP amp in my flair so all sources can be played back over speakers and/or headphones.

I'm a big Basil Poledouris fan as well but his stuff is harder to come by on stream these days. Bear McCreary also has some good ones, but also a few misses.

Last of the Mohicans has been a favorite of mine for many years. Should be available on most streaming services.

Oh boy you're gonna catch some flac/k here but DLtBGYD. Yes there can be a difference between lossy and lossless track but you may be hearing a difference in mastering. For me the Mix/Master>lossless/lossy>any codec/format "benefit". Maybe dial back the hyperbole and enjoy those lossless tunes. I am with ya there is no sense in discarding (perhaps worthless) data these days... lossless is cheap and readily available.