My wife's iMac6,1 has 2GB ram (2x1GB). We'd like to max it out and was thinking of getting http://eshop.macsales.com/item/Other World Computing/53C4DDR2P4GB/ Officially her iMac only supports 3GB max. I've read that 4GB will be way faster even though only 3GB is supported. Should I order the 4GB kit? Or keep one of the 1GB sticks and order a 2GB stick.