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.
HD11 Hegel DAC much better than H80 built in.
AZ silver reference very good.
It is hard to answer since it is always a system thing. Coax should be better but is sensitive to ambient noise and affected by transmission line effects (reflections in the cable). Toslink is immune to ambient noise and reflections but might suffer from the system noise, because of longer transitions. You have to check for yourself. In either case cable can screw-up sound by producing time jitter of the signal. Jitter will convert to noise proportional to signal level. When comparing cables look for smoother cleaner sound and better imaging.

Coax should be shorter than 1ft or longer than 1.5m. In first case cable is not long enough to produce reflections but in the second case it is producing reflections (from the end of the cable on impedance boundary) that will miss edge that initiated it (otherwise it might add affecting shape of transition)
Just purchased the Hegel 80 a month ago. Great Amp/DAC. I also have an OPPO BDP-95 and a REGA Appollo CD player. My key issue at the time of purchase: "cables" Compared coaxial cables such as the Audioquest VDM 1, basic $10 cheap coax cable, SCA-D1M from Tributaries, and Optical Audioquest Cinnamon. The difference was hardly noticeable between any of them on A/B B/A direct comparison. I then realized that a bigger issue might be coming from the speaker cables. My current cables were a bit muffled in mids and highs. Tried Clear Oval from Analysis Plus - clearer but lost a lot of bass. My dealer suggested Audioquest Go-4 but since I need 12 feet on each side, it would have cost me more than $800 (with the connectors). I thought, what the heck, let me try Anticables Level 2 Performance speaker cables and I also purchased the Level 4.2 Reference Plus digital interconnect with the Pure Harmony plugs. And then, WWOOOOWWWWW! The depth of stage, the tightness of the bass, the clarity of the mids and highs without harshness...Oh my God !!! It made my purchase of the Hegel really worth it, the whole system came alive. When you add 25 feet of speaker cables for $150 and the coax interconnect 4.2 with pure harmony plug at $185, with a 30 day trial period, how can you go wrong? but I doubt that you will return them. Best Bang for the buck ever. IF you have money left over, order a power cord from Anticables for your Hegel... and one for your Oppo and hear the difference