Unless you know you're going to need the extra memory headroom, or you're hardcore into the memory benchmarks, I wouldn't bother with anything PC2-9000 or higher. There still tends to be heavy price premium for them, and the stuff between PC2-8000 to 8500 will still give you enough headroom for 99% of any OC-ing you might want to do.
__________________ i7 2600K | ASUS Maximus IV GENE-Z | GTX Titan | Corsair DDR3-2133
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