Beyerdynamic DT990 600 Ohm user reporting in! Just received it recently, comparing it head to head with the HiFiMan HE-400 and will be deciding which one to keep.

Hmm, may I know why? They sound pretty good to me. I bought it to compare against the HiFiMan HE-400. After some burn in time I'll decide which one to keep.

They have different sound signatures though, the DT990 sounds something like my Grado SR80i, bright but with better soundstage. The HE-400 sounds dark in comparison. And yeah, I agree that the DT990 600 is hard to amp. Currently using FiiO E17+E09K for it. Might upgrade later to the O2/ODAC combo. Schiit Lyr would be ideal but its too expensive at the moment.

I've heard the DT880 a few years ago in your SS15 shop and I preferred the DT990's sound over the DT880. I guess that's why I went with the DT990 instead.

Yeah which is why I got the E09K as well to pair with the E17 to drive the DT990 properly. This is just a temporary solution though, I might return the DT990 and stick with the HE-400 instead.