Running CDP directly into MC275??

It better. You probably don't need even that. But its not bad to run your control all the way up. If you can clip the amp, you don't need anymore gain.
OTOH if that's not happening an active will sort things out.

My vote is no. I have tried it with several preamplifiers, and without on my Mac 2105 which has gain controls, so that the source isn't involved, and in every case, the sound was better with the preamp. It was better proportioned, and more dimensional.

^^ I've always felt an active sounded better too, and to the above comment I will add: 'better bass impact and extension'.