If I'm being honest, I think there was a deterioration when I switched to XLR from RCA, but I was trying to convince myself the XLRs were better! I'll try switching back to RCAs and see if that does the trick.
I got the XLRs from Blue Jeans cable, so I know they're well-made. Could it have something to do with the fact that my Sunfire amp is from 2000 and the Marantz Pre/Pro is from 2012? I found this thread which seems to pose the same question:
http://www.htguide.com/forum/showthread.php?30942-XLR-Polarity
