Howdy!
I'm a recent convert to the Concero, having purchased the original model to replace my old audio-gd DAC3SE. I've included a photo showing the size/scale difference between these two DACs! The Concero is a great DAC, with a bit better detail retrieval than the DAC3SE, but not quite the same tonality. I rate it very highly indeed, especially given the incredibly small form-factor.
I'm using it with a Squeezebox Touch and I initially powered the Concero via the USB socket on the Touch. It seemed to perform fine, but the main downside for me was the need to physically unplug the USB socket from the DAC each time I wanted to switch it off. I leave my Touch powered on permanently, but in stand-by mode with the clock showing on the screen.
The cheapest 'decent' option that I found was the Teradak 9V PSU which now comes with a 5V USB output too. The PSU also includes a 5.5mm OD/2.1mm ID power cable, and a USB 'power-only' cable with data USB piggy-back capabilities (if that makes sense!). The cost was around $60 landed to Australia. I believe there is a slight improvement in bass definition and the noise floor with the Teradak PSU, but it's a closely-run race. It goes to show how decent the regulator stages are on the Concero!
Using the 'power-only' cable means that the Concero automatically reverts to SPDIF input mode, whereas when it was powered via the Touch, I needed to cycle through the input modes via the Apple remote as the Concero would revert to USB input mode each time.
One interesting point to note is that I tested the noise levels from this PSU, as well as a few switchmode USB PSUs including an Apple unit, and a generic unit.
The apple unit was around 80mV noise, and the generic unit was over 200mV! The Teradak noise levels were indistinguishable over background noise levels. I couldn't measure down to microvolt levels though. Sadly I didn't test the USB output of the SB Touch. I will do this in future.
Overall, I'm impressed with this power supply given the quality of the build, the included cables, and the very slight percieved improvement in sound quality. The addition of a switch to power the Concero up and down is also welcomed.