My parents have a rev. a iMac G5 with 256mb of ram. They are going to be installing tiger on it and and they are going to be upping the ram. According to http://docs.info.apple.com/article.html?artnum=300082 there is a benefit of using matching DIMMs. How signifigant is this benefit in real world use? I was going to suggest to them that they buy a single gig stick but might it be better to purchase two sticks of 512? The drawback is that if a couple of years down the road they decide to max out the ram they will have to buy two single gig sticks instead of a just one.