Best Performance CPU upgrade for a R900

I currently have an R900 with the following specs: Intel Xeon X7460 @ 2660 MHz. Having 4 CPUs with 6 cores it gives me 24 cores.

I was wondering if there is any better upgrade than this CPU. I know the last 604 mpga released by Intel is the Intel E7525 @ 3GHz 800 MHz. And what is the maximum clock frequency that I could use with those new CPUs.

Also is there any GPUs that can be added to this system?