If we're talking about neutrality here, let's skip comparisons to hifi grade components. Why not high end studio gear from Lavry (Gold), Mytek, Solid State Logic, Antelope Audio, Apogee, Dangerous, Crane, Weiss etc. These guys actually make equipment that gets used in professional studios where music is made. Convertor neutrality is obviously a given. I have never ever seen an ODAC or O2 being used in a studio. Why is that? Are all these professionals just stupid to spend $10,000 on converters when they can opt out for a $300 ODAC+O2.
I highly recommend people to audition some high end studio converters just for fun. I guarantee that the difference will be huge. I have ABX and double blind before for cables and once with O2 and Emotiva mini (when I initially got it). Those seemed close initially in performance so I thought why not. Although with my current rig and other studio gear that I use from time to time, the difference is so huge in performance that it isn't even worth bothering with any testing. Of course this doesn't mean jack to you guys as you probably still want proper testing done….but seriously try high end professional grade convertors and you'll know within seconds.
You don't even have to go spend crazy amount. Even a Emotiva Stealth DC-1 will murder it. Ask anyone that has made that change and they will all pick the DC-1.