Memory upgrades availble for an l502x with the A06 bios

I have an l502x with the A06 bios which has the 2720QM and the stock 6gb 1333 memory. I just found a thread (http://forum.notebookreview.com/dell-xps-studio-xps/612534-l502x-ddr3-1600-1866-ram-2.html ) saying that the one person installed 1866 mhz memory into their xps 15 loaded with the same hardware/bios revision and it moved their WEI from a 7.5 to 7.9. My question is this- If purchase this memory, http://www.newegg.com/Product/Product.aspx?Item=N82E16820231482 , will it run at the set 1600mhz speed or downclock to 1333.

Thanks in advacne