Input Sensitivity

I have a Rotel Rmb 1095 , apparently it expects to see 1.5 Volt Input . My pre-amp puts out 1.2 volts on the unbalanced, and 2.5 volts on the balanced output. Would the unbalanced 1.2 volt be a better match for me , or doesn't it matter?. Also I have a very slight hum which is constant at any volume . I have read where the unbalanced connection could eliminate this.

The 1.5V is for the amp to deliver it's FULL POWER. You don't want that to happen. So you have the volume control to control the entire 2.2V that the CDP is delivering to the preamp. The preamp will start with 0 and go up from there. I don't know the specifics of your amp, but if your speakers are not sensitive enough, I suggest the Balanced over RCA.
Yes, Balanced will have a slight hum if your speaker are sensitive and your ENTIRE setup is not Balanced.