About the memory I found something interesting...
Form the 4.6GB at least 600MB is not to use from memory... it is supposed the be streaming directly from HDD (like dialogs) but Guerrilha is using a pool in memory... than can change in final build.
And about the CPU the guys in B3D are saying that the devkit was running at 1.6Ghz and Killzone using 6 threads... that information was analysing the profile output.