I have one of these and would like to upgrade the standard 512 ram. What's the bestw ay to do this. The apple store memory prices are huge! Would it be better to buy from another site or will there be problems. If it's fine does anyone know which sites in the UK are the best? Also, as it has 2 memory chips in already. If I remove one and add a 1GB, making 1256 mb will this be a problem as I've heard you should have each at the same size. Help would be appreciated.