You know who has the most cramped but most awesome setup everywhere?
NiHaoMike He cramped what is basically a full power desktop, atom system and a arm tablet-ish hardware into his ATX case
There's also a "triangle" power system in there as well. Think of the AC input, 12V battery connection, and regulated 12V output as the vertices of a triangle, with a DC/DC converter, front end converter, and battery charger as the sides. (Only the battery itself is outside the case.) All that is controlled and monitored by a PIC, so that the Atom subsystem can read how much power the system is using and perform advanced battery management. The PIC even has control over the large fan on the side, so that if it senses a sudden increase in power usage, it can rev up the fan before the components have time to heat up, allowing more Turbo Boost. (In practice, it can hold a full 3.8GHz Turbo on all 6 cores indefinitely even in a hot 85F room as long as the fan is at full throttle.)
And as packed as it looks, there's plenty of room for a second video card, at least two SSDs, and another HDD.