No USB input on my Hex, and it had stock output transformers. I think the output transformers on the Hex give it a slightly different flavor over the Quad (and I've read the same for Octave Mk1 or 2), which I believe are both more direct coupled to the output.
I'm not saying the Hex wasn't an improvement over the Quad, just that they're much, much more similar in the grand scheme of things when compared to the wide world of other DACs. Both were still the least resolving DACs I've heard out of the bunch I tried over a few months, even compared to the NOS1704 from Audio-GD. I haven't actually heard the Octave Mk2, but based on what I heard with the Quad and Hex, I find it hard to imagine the Hex really offers much over the Octave Mk2 in terms of technicalities unless you need stuff like balanced outputs. But, again, haven't heard the Octave Mk2, so I could be VERY wrong. Hex just strikes me as the type of DAC for people that have money to spend, where as the Octave Mk2 likely captures most of what the Hex offers but with less options and a much better value proposition.
It could also be that my JKSPDIF Mk3 coming from my PC source was the limiting factor.
Let's blame your source, indeed