Bigsam2, I have already Benchmark DAC1 with good headphone amp built in, but I bought separate headphone amp for convenience. DAC1 is across the room and requires long cable that is easy to trip over. In addition switching off main amp would require fiddling with switch on the back of DAC1 and possibly switching to wrong full volume position (I use its volume control - connected directly to power amp) or switching off power amp, that does not have power switch. My wireless server is next to my listening position and the best solution for me was to buy headphone amp/DAC. I got OPPO HA-2 and it is amazing with Yamaha HPH-200 headphones (another gem). It has asynchronous USB, SPDIF, DSD and analog inputs (I use USB). It has headphone and analog out. It uses SABRE 32 bit D/A converter and discrete output stage. Clarity is simply amazing (better sounding than Benchmark DAC1). It is also portable (has lithium battery built in) and works well with supplied ON-THE-GO USB cable with my android phone. My main computer is Mac Mini. It does not require driver. $300 is a little high, but it had great reviews and looked beautiful - wonderful packaging (I don't work for or sell them, in case if you wonder).
https://www.oppodigital.com/headphone-amplifier-ha-2/
https://www.oppodigital.com/headphone-amplifier-ha-2/