Is there a visible performance difference between 4 gb and 6 gb of RAM? Specifically with the CS3 apps...I have Photoshop and Dreamweaver open most of the day, along with one small app for Windows in Parallels. I have a ton of page-outs and I can hear the HD crunching at times. I have 2 gb right now...definitely going to add at least another 2 gb, but was thinking of buying 4 gb instead. Any similar experiences? I don't mind spending ~$400 instead of $200 if there is going to be a significant difference, but not if we are talking a minor difference.