I will be upgrading from my current ram of 1gb to 3b soon. I was looking at crucial ram but my question is can i just buy the 2gb to make a total of 3gb on my imac or do i need to buy the 1gb from crucial also? I guess I am wondering if they need to match each other or not because my current 1gb of ram is the one the imac came with but it just isnt enough anymore to many wheels of death!