Highest Possible Sound Quality from iTunes

[mobaer]

Also, it occurs to me that a simple solution would be to use a Mac of some sort, maybe with SSD, linear PSU, then USB to a Mutec MC3+USB, XLR to the Devialet.  I'm sure this would work (although F1eng had issues with a Mac + Mutec combo), but I am not sure if it would match a Melco or similar.  (does anyone know how good the SQ might be with this set up?)

But is there a better way?  What would be the ultimate solution?

I use exactly the setup, that you describe (except the linear PSU). Introducing the Mutec between Mac Mini and Devialet has increased sound quality a lot. By re-clocking the signal from the Mac it reduces jitter, and transfers the cleaned signal via XLR to the Devialet. For me it enhanced the three-dimensional representation.
I started using Audirvana instead of iTunes, because Audirvana offers the possibility to configure upsampling depending on the sampling frequency of the source material. I use this feature for upsampling my music in CD quality to 176,4 kHz. As a result to me strings sound a little more natural (just to give an example).
I would prefer Roon over Audirvana because of its user interface, but unfortunately Roon doesn't have an integrated upsampling engine.

In theory the ultimate solution should be AIR in bit perfect mode!
In that case you do not have to worry about jitter, because data transfer is asynchroneous and buffered. No clocking issues can occur. However, AIR doesn't work reliable in my case.
If the Devialet had a clock input you could synchronize Mutec and Devialet and by this eliminate jitter. The result should be the same as with AIR. Sadly, Devialet does not offer that option.

In a perfect world I would use Roon with upsampling feature (under development as stated by Roon Labs) and AIR in bit perfect mode. Until this comes true, I go the way that you described and I am quite happy with it.