Here's a solution for the graphic card via Thunderbolt.
Sonnet Echo and a real life test using RED and their
RED Rocket graphics card.
BTW for multiple graphic cards enclosure, there's
ExpressBox 3T. Which will house up to 3 PCi cards with only 2 Thunderbolt connection needed to your system.
The only thing that a tower might have over a smaller form factor system (iMac, MacBook Pro etc.) might be more core processor horsepower. However at the current stage in the game most of these systems will be more than fast enough for video needs. And with the advent of Thunderbolt, expansion for video and storage seem to be more than possible.
Yes there isn't much in terms of Thunderbolt currently, but give it a year or so, and I think that you will see a lot more. Even more affordable solutions. This seems to be what Sonnet seems to be working towards. Hell if you could buy a Thunderbolt Promise system without the drives, then this could save one lots of money. But currently Promise seems to be very greedy in only giving us solutions with drives installed.
Michael
Video Cameras: (2) Sony NX5U
DSLR: Canon 550D
Lens: Canon 50mm 1.8, Tamron VC 17-50mm 2.8
Software: Sony Vegas, Final Cut Studio
Computer: MAC BABY! MacPro, MacBook Pro