Hypothetically,

[StevieC]

The most extreme build achievable without actually overclocking the chips above the speed they were set to when the end-user purchased them

And I must give SNiiPE_DoGG partial credit for inspiring me on this, so if you notice any resemblance, credit where credit is due.

Also, yes I know this list is incomplete and I will edit to fill in the gaps as I manage to decide what to fill them with.

1x MSI 790FX-GD70 mobo
1x AMD Phenom II x4 955 Black Edition
1x Custom Built Phase-Change CPU cooler
4x Sapphire Radeon HD 4890 Atomic Edition in CrossFireX
4x Graphics Card WaterBlocks in Parallel
1x HT Omega Claro Halo XT (PCI)
1x BigFoot NetWorks Killer Xeno (PCIe single-lane)

[EnJoY]

Yea, I think you've got it. Although some would argue that dual-socket would be more extreme, but then you get into the argument of what's extreme and what's practical for a desktop setup.

Only issue I would see is this...why a phase change cooler for the cpu if you don't plan on overclocking? That just would be silly and decrease the 24/7 reliability due to the chances of condensation.