If one had to be longer which would it be?


speaker cable or interconnect to amp?
thegoldenear
In my many trials and tribulations, I have always found longer interconnects and shorter speaker cables sounded the best. I think I have always read that too. YMMV
It depends on your gear, including the wires themselves, how they'll be placed, and even your environment.
......and on the the impedance of the cables, the output impedance of the preamp and input impedance of the amp.....
It is intimidating, and possibly expensive. How long are we talking about? You CD player is single ended (not balanced) and might have issues with powering the longer cables to your integrated. My first guess on this is try to longer speaker cables unless you are thinking more than 15'/5m.