Best headphone amp under $400

Are you looking for just an amp an an amp/DAC?  I’m using an AQ Dragonfly Red from my iPhone to my HiFiMan HE400S and it works very well, but it’s just barely enough amp to get the job done.  If you can do with something a bit larger (but still portable) I’d recommend looking at the xDuoo XD-05 Plus as well.  Best of luck. 

I am looking for AMP + DAC in one package. I have read very good reviews of the AQ dragonfly. was looking at cobalt. DO you mean barely enough for high impedance headphones or just any headphone ?
thanks  

My headphones are around 30 Ohms and 100dB. 

My Dragonfly Red is good enough from my droid phone to Tin hifi T4 iems  but connect to hifiman he-4xx and it runs out of steam well before I do.