+1. To a laptop and docking station hooked up to multiple monitors
I think with a MacBook you can daisy chain thunderbolt displays ??

PSS. Xp mode is a virtual windows XP machine that runs inside of windows 7 professional It's great if you have older software that isn't compatable with windows 7 64 bit.
Raid is probably not necessary but google it and see if stripping r mirroring is something you specifically need.

The w520 is a great machine to use as a desktop replacement. I got mine with the docking station and havnt even thought about using a desktop again.