I would recommend you to switch to a Digi sound card if the NAD has a better DAC than your HiFiBerry sound card. So you no longer convert the signal with the HiFiBerry DAC and amplify it in the NAD, but can use the NAD’s converter, which may be better. When it comes to Digi sound cards, the Allo DigiOne and DigiOne Signature are probably the most high-end ones that we sell. Apart from that the cards from HiFiBerry, Justboom and IQaudIO differ marginally, but are cheaper than the Allo cards.
On our shop homepage you will find the option to compare all Digi sound cards we offer: https://shop.max2play.com/en/