I gave the PP6 a mixed review at InnerFidelity because to me it felt (and still feels) like a missed opportunity. I love some aspects of it, and see the potential, but I also get frustrated in using it. Specifically, the gain needs to be reduced. That is step one. My unit goes from silent to quite loud in a very small increment, and there's still a ton of unused range on the volume knob. I believe it is digital attenuation too, so we lose resolution by applying so much of it. This means the PP6 is actually capable of sounding even better, if we could crank volume to 75% or higher without killing our ears.
Fix the volume control, get rid of the "thump!" on power on/off, and transform the bass boost into something worthwhile, and the PP6 would be a spectacular product. I'd totally recommend it. As it stands, those things really detract from the experience.