Hello all....can I please ask if this is the right model of RAM for my early 2009 iMac? I've been told to buy a Kingston 4GB DDR3 10600 1333Mhz Laptop Notebook Ram SO-DIMM Memory. My Mac is on 2GB at the moment and is really really freezing up on me even though my hard drive is only half full. Can I bump it up to 8GB or should I stay with just upgrading it to 4GB? Thank you!!