$500 for that iMac is not bad.

Like I think I already said, I have the white version of your Macbook with 4GB RAM for now. It works fine for what I do on a notebook computer. I might have also mentioned reason I don't go to 6GB is with Dual Channel RAM you need a matched pair. To get 6GB you need a 4GB and 2GB stick so it will NO longer work in Dual Channel config. I have in many tests found Dual Channel ram to be faster. So as long as the 4GB is enough for Lion (it is for me) I am going to stick with it.