Don't laugh... I'm running a Pi2B and IQAudio DAC+.
I bought it after reading Marco's "Analogue Dinosaur" thread and was shocked how good it was. Prior to that nothing had beaten my old TDA1541 based CDPs, including Auralic Vega, Benchmark DAC2, Audiolab MDAC and a few others.
The Pi/IQ combo is very sensitive to its PS and I tried quite a few types and configurations. Oddly enough (digital lottery!) I prefer the IQ powered by the (supposedly nasty) 5v to 3V3 switcher on the Pi to being separatley powered by a fancy linear PS. I had to overcome some expectation bias durring that listening test!
I bought a KALI & Piano2.1 set and seem to be the only person who thinks they sound poor, except for one guy on Allo's website reviews who gave he combo 1*. The Allo stuff sounded very "mechanical" to me. I tried loads of power supply options and combinations, including shorting the onboard inductors. Nothing could fix the sound. On paper the Allo stuff should be much better.
This is why I am so cautious of buying stuff unheard.