It took a while to get my shipping label, which of course arrived while I was out of town, so it took even more time to ship my original device back. Once I did, it arrived at the Georgia facility at lunchtime, and a new one shipped out that afternoon, according to the corresponding tracking reports. So the process went as quickly as possible once I sent it back. The new device arrived rather unceremoniously sandwiched in foam, in the felt pouch (perhaps the one I'd sent the original back in), and covered in transparent protective film. And a plastic plug in the line out jack. No other accessories or documentation.
I confirmed basic operation, but no lengthy critical listening. Initial impressions from my complete-at-long-last desktop listening station were quite positive. Superior resolution compared with my MacBook's DAC was immediately noticeable with Airmotiv 4s. Also apparent after briefly listening with HD-650s is substantially superior sound from an Asgard 2 fed with the Explorer's line out compared with directly connecting to Explorer's integrated headphone amp. All of which is as it should be, although I was somewhat surprised at the A2's immediately apparent superiority. Pretty happy with the rig so far, and it seems well-matched. Although, for now, I'm mostly just relieved to have everything finally shipped and fully operational.
While the Explorer/A2 sagas were unfolding, I made yet another impulse upgrade to the stereo speakers of the family home theater, which now sports bi-amped PSB B6s driven by a Denon AVR-1712. Although I don't get the opportunity to do much serious listening there, it's nice to deploy the Explorer on that system, too. I've yet to carefully assess the impact of the upgrade over the AVR's DAC, but I presume it'll be discernible if not obvious. If nothing else, Explorer upgrades capability to 192 kHz listening, and otherwise seems reasonably well-placed in class with the downstream home theater kit.
So that's at least four high-quality listening applications I'm getting out of this source, which is gratifyingly versatile. Output impedance drama aside, seems like a good investment.