I used to have C2600 with DAC1. I upgraded to Moon 280D and it was significant. I also had MC 302 and Sonus Faber Olympics Nova Vs. I used Kimber Kabyle KCTG interconnects and bifocal XL speaker cables.
I auditioned Kimber Kabyle 12TCs and I thought they were horrible because the higher frequencies were harsh to me.
Hope this is constructive