The XLR outputs on theSCD-1 are a convenience; they're not really balanced. A power supply difference is the reason for the difference in weight between the units. Although it doesn't seem to be because of XLR vs. RCA reasons, I heard a definite, but quite subtle difference between them at the dealer's, in favor of the SCD-1--slightly fuller lower midrange. Cables seemed to be the same, and the dealer swore that everything else was equal. Since I didn't take the 777 home, I can't tell you whether that was true.