One unit that is a DAC/amp I have and use very regularly is the iFi iDSD MicroDac .. To my ears hold its own ( albeit with some "grit", looser bass and overall to my ears less defined sound) to some serious DAC /amps combo I have. It cost about $500 ... Will drive any headphones or IEM under the sun and "does" almost all PCM or DSD rates you would send at it.