Heyy, So my iMac is running on a 1TB HD and 4GB RAM and i am looking to upgrade the RAM, if i buy (x2) 4GB Cards does this mean in the 4 slots i will be able to keep the two 2GB's already in there which takes up two slots and add the two 4GB's which takes up the last two slots which makes 12GB in total and it will all work well? Is this correct? Can anyone also tell me cheap places to purchase RAM? Possibly a store or if not online? Thanks.