Id personally go for theese instead.
http://www.overclockers.co.uk/showproduct.php?prodid=MY-017-SA
They oc like crazy, and a bit cheaper. Of the two corsairs youve linked, the xms 3 is reputed to oc better than the vengeance.
No probs, my vengeance wont do it's xmp rating of 1600mhz 9-9-9-24 at 1.5v. Have to knock the voltage upto 1.575 to get it to run without crashing with the cpu @4.5ghz.
Those arctic white vengeance seem to use a lot lower voltage than what my kit is rated at. Would be good for keeping temps that little bit lower.