Save your money. There was a time when OC'ing memory mattered, but that time passed a good while back during pre-DDR3 days. You'll never see a difference in real performance with slightly faster timings. Here's a link to a good chart, unless you can tell the difference between a couple of nano seconds then it's not worth it.http://i1013.photobucket.com/albums/af254/Jaquith/CAS_Frequncy_Chart.png[\IMG]
If you're still determined, bump up your RAM voltage to 1.63 (1.65 is safe max), and start lowering your timings bit by bit to see how low you can go with your kit. My guess is you can probably hit a safe CAS 7 with that RAM, maybe something like 7-8-8-24 or so at 1600MHz. You could also go the opposite direction and check 1833MHz and 2100Mhz OC's with slighly higher timings to see what's up. Use the chart as a guide, and then run some benchmarks to see what you get.