You will get very little if any improvement when using DX as a DAC instead of the Denons built in DAC circuitry. Same as for the amp. Now I don't have experience with Schiit amps, but I've compared my own <500$ headamps and many more expensive DAC/amp combos against receivers and integrated amps, and they didn't perform as well. High impedance cans, mainly the 600 ohm beyers absolutely LOVE the outputs of integrated and receivers, because they can get virtually limitless power out of them.
So if I understand your post correctly, I will not gain any noticeable quality in sound over just using my receiver alone?