I re-read my post and realized I was a bit unclear in the end. I did go back to the HD6XX, but I decided to keep the Arya V2s as well. That said, for people who decide not to upgrade at all, I learned (from this $6000 journey) that decision is totally justified. We get used to whatever headphones we have -- and the HD6X0s offer more than enough to appreciate.

I'll give SoundSource a try -- thanks for the tip. It is a bit frustrating to have to input everything manually in eqMac...