If all you can go with right now is 4GB then go 4GB. Just make sure you do it in such a way that you can add to your existing memory when you make the jump to 8GB. That is, if you have 4 memory slots, dont fill them all up with 1GB sticks. Sounds dumb, but some people do that. Fill up 2 slots with 2x2GB sticks and then later you just pop another set of those memory sticks in later when you can afford them.