I received the Quattro II today and tested it on two PCs:
a) my laptop w/dock at work, where it replaced a Topping D50 + Schiit magni3. This unit is definitely an improvement here, the whole sound felt wider and more expansive. I really enjoyed it. This was solely through my headphones mind
b) my desktop at home straight to USB, where it replaces a Schiit Jotunheim w/ DAC. Mostly I wanted something smaller which didn't run as hot as the Joti, and had a remote. The Quattro II does all of this. On this PC I barely ever use my headphones (HD6XXs)
The Joti did two things better:
* I could connect the headphones at the same time as the speakers, which meant I didn't need to keep them unplugged to hear music. Useful to burn-in headphones if that's your thing, or even just for convenience
* The volume control was a lot less gradual and WAY easier to use
The Quattro's volume control is way to grainy, and much tougher to adjust. I feel it's overkill in this respect. It does run cooler though.
Another issue... THAT one is a big problem: my unit lets out some noise through the headphones. They sound electronic in nature. I've had this happen before and it eventually went away; I'm not sure what I did to help it. Weirdly, this did not happen on my laptop, but does happen on the PC. I will try different USB outputs, or maybe the spare Schiit Wyrd I have.
I think this may become my office setup actually, as I'm still waiting for the SMSL SU-8 and the HPA-3 which will become my home balanced setup and, I hope, fix these issues.