This amp is amazing. It's quiet, dynamic sounding and powerful. Look at the specs! Most modern amps that cost two times more don't have specs like these. Noticed the output impedance? yes, that's 0.25...
K67 is perhaps the best sounding "bass" headphones for under $100. It's not crazy boomy like most, it's actually musical and sounds good for music genres outside of EDM and bass music.