Thanks for your posting, I'd been kind of curious about what happened to SPL !
It looks like they're more noticeable in the "Pro Audio" world then they are for home audio these days. I'm not really interested in tubed headphone amps as they place an emphasis on "Ambient" sound over the sound of the music being played. This "works" well as an "enhancement" for a lot of music, but it really doesn't "work" for large scale, dynamically dense music that already has a natural "ambient" sound balance !
The Phonitor mini looks like it might work pretty well with my Metrum Hex DAC (I'll be able to use the Balanced outputs) & "modded" Sennheiser HD800 phones(Which work so well for me, that I believe will be my "Endgame" headphones).
This SPL amp is going on my "want" list, as it comes in at just a bit more than half the cost of other headphone amps I've been considering
