@Uber.. wow, excellent pointer (from the Man himself!). That's a tiny and restrictive case, but that of course is the fine niche I'm aiming for. The Silverstone site is rather annoying to navigate with Flash everywhere, but it may be that you can use DUAL double-width cards which would be rather incredible. Now I need to dig deeper and learn about PSUs and such too.
@compu: budget is pretty high, since it's for business and it's better to do things right. These days it's rather hard to spend a lot for a PC though.. (Well, sure you could RAID up some Intel SSDs or whatever if you really wanted to boost the pricetag.)
The SECOND box I'm planning to build at the same time is a full size tower. It will use a Foxconn Destroyer with 4 Nvidia 295GTX boards in it, similar to FASTRA http://fastra.ua.ac.be/en/index.html
, a machine built last year by another GPGPU research team.
But for this one, my main criteria is "the most powerful box that fits in airplane carry-on and is also one-handed luggable. A shuttle case would be great, but that Silverstone may be give the best flexibility.