My new Atom HE will be winging its way to me in the next few days.
I’ll be connecting my Marantz CD6007 player to it.
The Marantz has optical, coax and Line Out outputs - the Atom HE has the same inputs.
Which option is going to give me the best sound quality please?
As Paul says, you’re in a good position to try and let us know what you find. But I’d expect digital out from your CD player to sound superior to analogue out as the Atom digitises analogue inputs. Between coax and optical, I’d bet on the former, but it may depend on the optical cable you use as cheap ones can be pretty low quality, especially the Toslink plugs used.
I wouldn’t spend big money on a coax cable. I’ve used Nam DC1s in the past, which cost as much as your CD player. I find that I get just as good performance from much cheaper cables - I’m currently using a Mark Grant HDX1 which cost about £30, and I have a Gotham which also worked well.