I just got an Explorer2 a few days ago, and have been giving it a listen. I've mostly been using it plugged into the little minijack "A2" input of a Meridian Prime, comparing the Explorer2 as a DAC to the Prime's built-in DAC and to a Schiit Bifrost (the latter with the latest audio and USB boards). Where it gets weird is that I'm most often not using headphones plugged into the Prime; I'm using the Prime as a linestage which drives a little Parasound power amp, which in turn drives a pair of Audience's The One speakers. So my setup is kinda weird, and your mileage on entirely different roads may be seriously different.
Plugged directly into a USB port on a Mac Mini, the Explorer2 sounded a lot like the Prime's DAC, but lighter-weight. It was genuinely pleasant, but wasn't up to the standard I was used to.
Plugged into a Schiit Wyrd, the Explorer fleshed out and started to sound shockingly much like the Prime's DAC section. I highly recommend that combination. I haven't tried any other flavor of USB cleaner-upper/power-supply replacement with the Explorer2.
Comparing the Bifrost... I continue to respect it, and for all I know is may be more "correct" in some sense, but I tend to find myself preferring the Meridian D/As for the music I've been listening to most these days - mostly jazz. The Meridian sound feels more organic to me; when I switch to the Bifrost, it's as if somebody switched on a light with slightly too high a color temperature for the atmosphere in the club I've been in. I've been finding the sound of both Meridian DACs more engagingly musical to me, and I listened to the Explorer2 quite happily. I could listen to it as a line-level-output DAC long-term without feeling I was deprived. I'm seriously impressed with it for the price - although I'd recommend budgeting another hundred bucks for a Wyrd.
I haven't done enough listening to the E2 driving headphones directly to pass judgement on its chops there.
And I fully acknowledge that my Meridian-vs-Schiit impressions here may be influenced by the greater amount of time I've spent listening via the Prime's DAC than via the Bifrost, and whatever acclimation may have happened because of that. May be.