Whatever sounds better and what the manufacturer of your DAC recommended.
I have a LessLoss R2R with the outboard 640X firewall and 3 inboard. Also use a Innuos Zenith with the Sense software. Zafino Cable USB. No clock as there is no need for it. I also do not use MQA as it a bet of a joke in my opinion. Use Quobuz for streaming and mostly radio..Pardise. .1FM.
Sounds spectacular in my system. Lower grade stuff will require more insularly items to make your digital sound better. DDC, Clocks, ….just my options so take it with a grande and use what sounds best to you.