You seem like you really wanna buy an iMac, so I doubt there's any dissuading you on the worth of that, but as others have said Final Cut Pro should play OK on a MacBook, it's the other applications in the Suite that will struggle. I don't know if you're going to be using them much... And if you're only editing DV, Final Cut Express can do most of what FCP can for a lot less cash.
The thing I would really recommend though is an external hard drive to keep your footage on. Running the application and streaming footage from the same disk is going to be a real bottleneck and waste a lot of the money you've spent on a powerful computer.
The thing I would really recommend though is an external hard drive to keep your footage on. Running the application and streaming footage from the same disk is going to be a real bottleneck and waste a lot of the money you've spent on a powerful computer.