R710 and R610 memory upgrade and speed

Hello, 

we're going to upgrade the RAM on our VMware hosts, that are a mix of R710 and R610 servers.

We need to have 16 GB modules in order to reach the amount of memory we need.

We already asked Dell Italy for the spare parts but they say that although the memory modules exist, they ARE NOT GUARANTEED TO WORK BY DELL.

Some questions:

- Is it really true that there are actually no 16 GB modules guarateed to work with those systems (@ 1333 Mhz), or are they wrong here in Italy?

- I know that there is a limitation on the system memory speed at 800 Mhz at certain conditions (memory ranking, ... and so on); what is the BEST combination of MEMORY SIZE and SPEED? I would not like to buy the memory and have a system with 40% slower on the memory throughput.

- I found this memory. Given the description I expect they SHOULD work, but at 800 Mhz, right?

http://www.ec.kingston.com/ecom/configurator_new/partsinfo.asp?root=&LinkBack=&ktcpartno=KTD-PE313Q8LVK3/48G

Thank you for any help!

Kind Regards,