Not sure if this should go here or elsewhere, but for the curious, and since I’d asked, it’s possible to power an A+ / iQAudio combo from the USB port on the back of an Addon C10.
The reason I went through the trouble was that I wasn’t sure there’d be enough juice to power a full-size B+ and a DAC HAT. The A+ is cheaper, smaller, and draws less power, and because the Addon’s USB is specced at 1A, I figured it’d be better to try to minimise current draw.
Because the A+ doesn’t have an ethernet port, you need to get Wifi working before plugging everything in. So configuring Wifi is the toughest part.
The quick and dirty way to do this is to use a “regular” pi (I had a Pi 3 Model B+, i’m not sure if it’d work with older models), and then swap SDCards. @spockfish, if there was a way to document how to do this (more) cleanly, it’d be fantastic.
One minus of the configuration is that USB power doesn’t stay on - when you turn the speaker off, it’ll power down the Pi with it. An IQAudio DAC is probably overkill, SQ-wise, but hey, at least, you get Roon Ready, Roon controlled volume (yes, really, @Kii_Audio 
), and glorious 384 kHz to make sure your neighbourhood bats get to hear the transients on Best of Nosewhistle, vol. 25 (plus, because the C10 is mono, it’ll only trigger your tinnitus in one ear, anyway).