It really does sound like bad RCA'a or a bad RCA input jack.

By chance is there a set of RCA outs from the deck not being used? They might be grounding on something back there if they're not covered.
Just fishing for ideas....

 

Thanks for all of the suggestions, the amp is only a few weeks old, I would not think that the input is bad on it, and as far as I know the RCA' s are good. He has taped off the RCA's coming out of the deck, and has taped off the Auxiliary input when not in use also. Maybe I should get a set of Monster 201's, or some other nicely shielded ones for him to try out.....

 

Alright, thanks Paul! Will let my brother know.