Setup: iTunes ALAC --> optical/TOSLINK cable --> Schiit Modi 2 multibit DAC --> APPJ tube amp --> Sennheiser 6xx headphones or HiFiman HE-4xx headphones.
I've only been listening for about an hour now, but so far so good. The sound is deep and rich while maintaining mids and accentuating highs. I bought some Mullard NOS preamp tubes and 6v6 replacements, but haven't used them yet. I'm sure they will add even more depth and clarity to the sound.