Re digital v analog, I hope you are not thinking of plugging a DAC into the 'phono' inputs. This is a NO NO! A phono input has a built in equization designed for phono cartridges. Then there are gain issues to consider.
Now if your Marantz (with which I'm not familar) has no phono pre-amp, just different names for line stage inputs, a DAC will always sound like a DAC. Some units have a 'direct input' stage to bypass other features on the pre-amp which might effect the sound, but none that I'm aware of that will make a DAC sound like a Phono.
Re speaker cable. Welcome to the discovery, however a cautionary by way of example. Years ago I bought some highly touted cable and I was absolutely thrilled with the obvious 'improvement' in the highs. Just fantastic clarity. Then one day I realized that this improvement came at the expense of the bottom end which was eviserated. Take your time in reaching conclusions. :-)
Now if your Marantz (with which I'm not familar) has no phono pre-amp, just different names for line stage inputs, a DAC will always sound like a DAC. Some units have a 'direct input' stage to bypass other features on the pre-amp which might effect the sound, but none that I'm aware of that will make a DAC sound like a Phono.
Re speaker cable. Welcome to the discovery, however a cautionary by way of example. Years ago I bought some highly touted cable and I was absolutely thrilled with the obvious 'improvement' in the highs. Just fantastic clarity. Then one day I realized that this improvement came at the expense of the bottom end which was eviserated. Take your time in reaching conclusions. :-)