I also wanted to reaffirm what others have said about different SRAM chains. I've used a variety of them have noticed little difference in terms of shifting reliability and longevity between the lower cost (PC-59, PC-69, PC-950) and more expensive (PC-99, PC-990, PC-89R) SRAM chains.
I've had a PC-99 on my cyclocross commuter bike for about a year now, prior to that I had a PC-69. I've noticed virtually no difference in terms of overall performance and durability. The PC-69 lasted about a year/3000 miles, and I have about the same time and mileage on the PC-99 and it's about ready for replacement.
The more expensive chains are built with racers in mind. You are basically paying for lower weight, and in most cases this is only important to racers. For those of us who are commuters and recreational riders, 30-40mg less weight isn't worth the extra $20-30.