I agree on the TA-26 being fine, but not more. It's comfortable to use, it looks super cool, it maybe changes sound by a tiny amount, most notably dynamics and sub-bass, but not by much. My 6XX can also sing when hooked up to my FiiO K5 pro.

The TA-26 is definitely entry, I know, it's ridiculous, but some headphone amps cost more than a thousand dollars.

However and thank God we have audio demos on YouTube: between a few tube amps, cheap and expensive, I could mostly not hear any difference and if there was one, then it was so subtle that it makes no sense at all to spend hundreds more for a slightly different sound (different, not better, very important). So that's why I will continue being a sceptic and stay away from chasing minimal improvements. It's really not worth it.

What I'm curious to experience is to hear how my tubes will change once a lot of time has passed. I don't believe in any burn in stuff, but tubes definitely change, some even stopped humming after I let them run for a few hours and I'm pretty sure some infamous vintage tubes are only desperately searched for because some people heard tubes close to the end of their lifespan, adoring how soft they sounded.

But I'm done for now. Enough headfi snake oil reviews, enough overexaggerations on YouTube. I listen to music and not to my headphones.