This is where I'm clueless: my Grado SR80 are 32 ohms and my Shure 840 are 44 ohms. What should I be looking for in terms of specs in a amp?
Wiggy
Wow ok another US made tube amp yet to make it to Aussie shores 
Never heard it so I cannot offer up much advice with the HT1 ~ the others though are a matter of preference but I've never been a fan of the
Schitt sound.
Are these the specs you're seeing on the HT1?
35 Ohm Output Impedance
50mW Output Power into 30 to 300 Ohms
Bit of a worry for future headphones if those specs are true. 50mW means it's no powerhouse but more what is more of a worry is
the output impedance of 35ohms, this will play havoc with the 840's frequency response. Anyone who has used the Fiio E9's 43ohm
output 3.5mm jack with most $200-ish headphones will attest that it sounds pretty crappo.
