XLR or RCA?

The real benefit of using XLR cables is in the fact that it allows you to utilize fully differential equipment designs, which will lower the noise floor. That being said, just because you are using XLR cables does not mean that your equipment is a fully differential design, it could be a single ended design that simply has XLR inputs and/or outputs on the unit for flexibility. If the unit is not a fully differential design, you will not receive the benefits of running XLR cables.

Also, yes, to receive the benefits of running fully differential, you should run all the way from source through amplifier to maintain this 'advantage'. Any break in the chain, anywhere in the chain, and using XLR interconnects becomes rather pointless.

According to the McIntosh website, neither the C2300 nor MC275 are fully differential designs. The XLR inputs and outputs are simply cosmetic, therefore should hold no advantage.

No worries Al, I am sure that you are right. I would not disagree with you. I am simply repeating what I have been told, it could very well be misinformation, as this hobby is filled with it.

To be honest, I have gone both routes, running a fully differential system with all XLR cables, and running all single ended with RCA's. I cannot say that I have had a noise issue with either. I think I may have convinced myself the balanced was quieter, when I had it, but now that I'm back running SE again, and have no noise issues, I'm convinced I was just buying the hype. ;)
There may have been more measured noise, if I had the proper instruments to measure. If there was any difference in noise level, it was not audible, to me anyway.

I do agree with Mofi that the XLR connectors make for a superior connection though.

Elegal...no need to send LP's, that's why we're here....unless you have extras laying around that you are just looking to give away. ;^)