What's wrong with the Octave? Aren't you fully happy?
I also went in a Dac deathmatch in the last 4 months during which I owned the Reference 5.32, NFB-27 and, recently, the Concero. So far the Metrum Quad survived them all ;)
Will have to investigate with the Concero on a laptop in native mode (no remote) to see how it partners the Quad.
I'm really considering the Octave mkII which would be a double upgrade and all-in-one solution I am after (yet with proprietary drivers...).
The cost mainly; Octave + transport price is dangerously close to very competent options (audial/lampi/NFB-7 + exa i2s ...). The Mk2 price is (IMHO) even worse. You're better off with the old octave on special offer and a AP2/JKSPDIF. Sound wise the Octave has it own flaws, but nothing I can't live with.
My prediction is the Concero will make a decent transport for your Quad. But if you don't have the upsampling filter, as a Dac it'll feel a bit "dim".