TL;DR: for $100/$120 the Schiit Fulla 3 is an option, supports mic, powers HD6xx, won't get insanely loud. Between $150 and $250 there are tons of options, almost none of which support mics.
First questions: how much are you willing to spend, and
are you listening critically? Your suggestion of the Topping D30 DAC and Atom amp suggest a budget around $200-250?
Schiit have just announced 2 new entry-level DAC/head-amps with microphone support, which they classify as "Gaming DAC/Amps" on their site - the Fulla 3 (their true entry-level DAC/Amp, $100+shipping on their site, $120 on Amazon) and the Hel (more power, supports stereo mic, $190+shipping on their site, not on Amazon yet). I have the Fulla 2, the previous version, which is ... okay, it drives my HD6xx headphones much louder than my computer's onboard audio, and the audio quality's much better ... but I also have an iFi iDSD Nano Black Label, which is $200 on Amazon and which is
clearly better than the "I'm Fulla Schiit" (which is the actual name that it reports in Windows 10!). For $120 delivered, with mic support, there aren't many other options.
Audioquest also make a USB DAC/amp called the Dragonfly Black; it's $100, well-known and well-reviewed, might not have the power to drive the HD6xx loud enough.
In the $150-$250 range you get a *lot* of options. You're not going to find much with mic support in this price range, but there are lots of good DACs and amps:
- Schiit also make a $100 dedicated DAC (Modi 3) and $100 dedicated headphone amp (Magni 3), which when paired together are commonly known as the "Schiit Stack". Figure $250 including shipping and cables. These have a pretty good reputation.
- JDS Labs Atom amp and OL DAC
- Topping D30 DAC and A30 amp (note: the D30 is
DAC only, you will still need an amp).
- Audioquest Dragonfly Red DAC/amp. Widely beloved. Small, portable, should have enough power to open up more of the HD6xx' potential
- going up to $300 gets you an Audioquest Dragonfly Cobalt. Their newest DAC, people are saying good things so far.
- the iFi iDSD Nano Black Label - $200 on Amazon. I have this, and it was a big enough step up over the Schiit Fulla that it made me want something better than the Fulla for my stereo speaker setup.
I'm in a similar position to you, looking for a DAC under $200 for my stereo setup (speakers, not headphones) so I am doing a lot of research right now
.