Yes.
Is that a E6600 (dualcore) or a Q6600 (quadcore)? Either way you can just overclock it a bit and get a pretty decent boost. You should run the game pretty well even if you don't though. Wouldn't worry about upgrading or anything, though a quadcore certainly helps the situation. Edit: Also the 9800GT is worse than a GTX260, not sure why you would want to do that.
You quite honestly don't need to spend even close to that much. You could get away with spending about $400 (if you have a monitor/kb/mouse/etc) and run the Beta, and in turn Retail, perfectly fine.
Your Macbook has a 9400M or a 9600M right? Neither are even the minimum requirements for the Beta or the Retail game. The 9400M is pretty low end (think: slightly > integrated). The 9600M is about 2 years old now and even then it wasn't close to top of the line (in between 9500GT and 9600GT). I know you love your Mac and I don't have any problems with that. Expensive doesn't mean top of the line though. Mac's have been lagging behind pretty hard in the graphics card department for a really long time now. They are just now starting to include real high end cards in Mac Pros.
Despite what I've said, if you have the 9600M, I'm willing to bet the game will run at a low res (1024x768 or something), with most graphics settings off/toned down, decently well though. Probably not 30fps everywhere but you'll manage. Don't think the 9400M could though.
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Edit again because I was doing all the other questions anyway:
A 4800 is better than a 5570 by quite a bit. To let you know: the 5700s are usually comparable to the 4800s... not exactly sure why they aren't in the benchmark but owell. A graphics card upgrade would do you well anyway.
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