This was a few years ago, but from what I remember this is what we did:
We only listened via the digital i/o thru standard converters in the house (Lavry D/A and HDCD A/D). We first listened D/A with pre-existing files, switching cards after each playback. Then, we'd create a file for each card through an A/D conversion, same source, same converter, and played it back through a single card/converter, switching in the software. Then, as the list became shorter, we lived with each card for a few days and a few sessions to get a working appreciation for it.
Taking separate notes, Joe Palmaccio, David Smith and I came to the same conclusion. Then we set up a scaled back listening session for the others.