I have used my FiiO K5 pro ESS and the TA26 and I think they are very similar to each other. The TA26 improves the low end a bit and maybe, just maybe makes everything a little more dynamic. But the changes are so subtle that there is almost no difference if I'm honest.

Also, the TA-26 suffers from potentiometer crackling, an issue nobody talks about in their fancy reviews. I swapped it once for a better potentiometer, soldering and all that, but the issue persists.

I still love this amp, but it sure is not what the reviews say. Tube rolling makes not much difference on the TA-26. Tung-Sol, EH Gold, RCA NOS, Foton 6H8C's from the 60s, JJ 6SN7.. They all sound very similar to each other. The NOS tubes are a little bit less punchy and flatter, but still so close to the rest that any differences are highly debatable.