The macbook pros were just released and you could take it to class with you. Then when apple gets its act together some time in 2013 you could look at the "new pro." (or most likely sooner the new imac or new mac mini).
MacPro4,1 2.66GHz 8 core 12gigs of ram. GPU: Nvidia Geoforce GT120 with Vram 512. OS X 10.6.x; Camcorders: Panasonic AG-HPX170, Sony Z7U, Canon HV30/40, Sony vx2000/PD170; FCP 6 certified; write professionally for a variety of media; teach video production in L.A.
Personally, I'd go with the 2 drive system. The second drive is always beneficial (I use a 2011 MBP and I wish I could have 2 drives along with the disk drive. I just use a few externals for backing up important stuff). Get the lowest end HDDs in the 2 drive and replace the boot drive with a small SSD. Then use one as a backup drive and the other for storage. Just don't get your SSD from Apple. I've used Lion Server and nonserver I really haven't noticed much difference. If you need people to be able to remotely connect to you, go with server, if not, don't bother. As far as adding drives, If the config page on Apple's site doesn't let you choose to add a second drive, or select none for the 2nd drive, you won't be able to. Hopefully that helps.