Best Headphone DAC/Pre-Amp?

I'm a HUGE fan of Oppo's DACS,truly world class IMO.At the price point of the HA-2 I don't think you can do better.Great choice.

These are VERY low impedance cans.I’m not sure of all in one units but for a 2pc.kit I HIGHLY recommend the SABRE DAC2 from HiFiMeDIY(Chinese under a Hundred $ delivered)like I have in my headphone system with either a Little Dot 1+$150.00...Schiit Audio Lyr II $450.00 or Woo Audio WA6$650.00...Stay away from the OTL All Tube amps,they are no good with low imp...Head-Fi.com is a fantastic place for all things headphone.

What is your budget?Are you looking for the crystal clear SS sound or do you want a bit of tube glow?