What absic said. I've been able to run my 2 sticks of RAM at 1600Mhz no problem, either. Could even overclock and it all stayed stable. It's just that, one day, you may find yourself with a machine that's not working anymore. In the end, it's up to you if you want to take the risk or not. The performance difference is really small and depends on your CPU-NB overclock, too. Wasn't worth it for me.
Remember, if your IMC fails then you'll have to replace the whole CPU.
