Don't bother, the performance benefit of increasing your RAM speed will be negligible (AT BEST).

And yes, these Ballistix are just repackaged PC2-6400 chips. But they've been tested to run at PC2-8500 speeds.

You see many show SuperPI benchmarks because that's the only program that shows a measurable difference in performance. So if you wanted maybe 2% gain at calculating pi to 1 million digits then go for it.

Otherwise, put that money into something more worthwhile like a graphics card/hard drive/CPU.