Best cables to utilize Dac in Hegel 80

In process of purchasing a Hegel 80 and really want to know how to get best sound out of the DAC in the Hegel. I will have it connected to an Oppo 105 and most of my music will be streamed via Oppo/computer but I want to utilize the DAC in the Hegel as better. My question is am I better to get RCA cable or go optical? I was told that you would get better sound quality going optical rather than RCA? Looking at purchasing Nordost speaker cable and cable. Pretty new to all this so a little confused. Thanks for your help in advance.