Hello, i am wanting to upgrade my pc's ram from 1gb to 2 gb. atm i have two sticks of 512mb plugged into two of my mobo's 4 slots. my mobo supports up to 800mhz ram. it is the gigabyte 965p - ds3. the ram i have in now is running at dual channel 533mhz. i was wondering if it would be ok to add in another two sticks running at 667mhz on the other two slots? or would i have to keep to the 533mhz? Thanks.