My system situation has recently switched to ddr2, which im not completely sure about. Can you mix ddr2 (samsung) 400 2x256mb pc3200 with say Corsair 2x512MB DDR2 Value Select PC5300 Dual Channel Kit to equal 1 and a half gigs of ram? what are the key things that must match? The PC3200 will limit the other rams speed? But do the Clock speeds have to match - the Corsair being 667mhz. Looking to spend no more than £100 on additional/replacement ram. Is value ram my best option?