I actually only need a DAC - the Bryston BHA1 is a first tier dedicated headphone amp - just no DAC. In fact some of my limitation is that the Grado and Bryston both use balanced XLR cable connections between headphone and amp. So I am really just looking at a DAC - that would sit between the PC and the Bryston. Likely USB to PC and RCA (or ideally XLR - but not likely without going high end) to the Bryston. This is why I was considering the new AQ Dragonfly or similar (only one cable from DAC to Bryston).
I welcome your feedback, and the DACs you listed are very attractive if I had no amp (and had standard headphone connection).