Jessica –
Recommended memory is at least 1 gig per core – in your case 8 gigs, at a minimum. More is always better.
You’re getting a lot of monitor real estate – The apple monitors are expensive, I would suggest looking at Dell and HP alternatives – high quality at almost half the price. The type of monitors you need will also depend on whether or not you are getting an I/O card.
You don’t need an I/O card but you will be stuck monitoring within FCP using the cinema desktop – not the optimum way to go. I’d recommend getting the best I/O card you can afford – you might not need the AJA Kona3 (around $2500) but if you have $1500 the AJA Lhi; otherwise Blackmagic and Matrox have less expensive options.
Cal Digit makes excellent drives, however you didn’t say which of their drives you are looking at. For a setup like yours I would recommend a protected raid set, typically raid-5. This will require a raid card as part of the package. You can get away with firewire drives, but it would be pennywise and pound foolish.
Something else to note – Apple is going to be coming out with a revised MacPro in the coming months based on the new intel i7 chips. If you can wait to buy till after they come out, it might be worth your while.
Herb Sevush
Zebra Productions