AMR DP-777, what am I missing ?

There are a lot of people here who love this DAC, I purchased one (used) based on the many glowing reviews, but feel like this DAC falls short.
To be sure it bested (by not a lot) my Wavelength Cosecant (better imaging and bass) but I still prefer my modest analog setup (Rega RP6, Shelter 500).

I am sure my digital front-end is not super tuned: IMac, audirvana, no-name USB cable to DAC. But before I spend more money I would love some advice from the good folks in this forum on how I can make this $5000 retail DAC at least come close to my modest analog setup that cost much less retail without spending too much coin.

Do I need to invest in a music server, or maybe a USB to SPDIF, or better USB cable or all of the above.

Rest of my system.
Coincident Line stage
Coincident Dragon mk2 monoblocks
Verity Parsifal Encore speakers.

Thanks.