upgrade advice

[ard-tullaich]

Hi, My setup is overclockers pc with a x58 ud5 board 920 overclocked to 3.8 and 6gig off corsair ram .
I'm wanting to upgrade to 12gig do i buy the vengeance 12gig kit
http://www.overclockers.co.uk/showproduct.php?prodid=MY-294-CS&groupid=701&catid=8&subcat=1389
or add another 6gig kit
http://www.overclockers.co.uk/showproduct.php?prodid=MY-205-CS&groupid=701&catid=8&subcat=1389.
Will i have to down clock my cpu if i fill all the 6 memory banks
Cheers