I have a R510 with 8GB (4x2GB ECC 1333 MHZ single ranked RDIMMs) with 2 E5620 CPU's.  I want to get the memory to 24GB. I would like to add to the memory and not have replace what is in there if possible. What do I need to get?  I'm confused about the memory configuration with  dual processors.

Thanks for your time.