I’ve thought about upgrading amplification, i haven’t committed yet.
They are being powered by Pass XA30.5 currently. I’m currently thinking Pass XA100.8 as the upgrade, though X350.8 has been recommended, but i wanted to stay in class A.
I’ve heard good things about the Atma Sphere line.
I’ve done many side by side comparisons with tube headphone amps vs my DIY Dynahi amp (overbuilt class A solid state) and always preferred the Dynahi. Thus i’ve never seriously looked at tube amps.