Also I should note that shifting is better with the KMC X10SL compared to the SRAM PC-1031. It's faster whether going up or down, front or rear, and less 'grunch' when shifting the rear under power.
However, to be completely fair, I also changed my cassette from a SRAM PG-1070 to a Shimano Ultegra 6700. I now have quite the frankenstein drivetrain: (2011 2nd gen) Rival shifters, 2013 Red FD, Rival RD, Ultegra 6700 cassette, KMC X10SL chain.
It works awesome, however. Big
to KMC for their part in it!
My next upgrade is probably 2013 Red cranks, but I would want compact and for there to be some availability of 52/36 rings.