DongulusWell the O2 isn't necessarily portable either. At the moment I have the Aune X7S which is arguably overkill for me. I'm only using SE at the moment but I have ordered a couple of 4 pin balance XLR headphone cables for my HD6XX and 58X. This one here (currently out of stock): https://customcans.co.uk/s/s/index.php/cables/original-sennheiser-cable/basicxlr.html Even though the Atom doesn't have balance output I'd be curious to see how they compare to each other.
DongulusThanks for the links. The Atom seems to receive good praise. However I'm not sure I would really notice much difference between that and the Massdrop O2 amp.
Mark_MHaving been in the same position as you and went with the atom, I would wholeheartedly say you should get the atom. I probably wouldn't be able to tell the difference between the two amps on sound alone, but I know for a fact that Massdrop's customer service doesn't even compare to JDS Labs'. If you have any questions on the Atom I can certainly try to help!