Yeah, the main reason I'm getting it is just because I can...
The challenge itself is worth the extra expense.
I've been doing a fair amount of reading on the Overclockers.co.uk forums, and I definitely think now that an all-in-one kit isn't the best solution. I'm going to get the parts seperately and make the loop myself.
One thing that I'm unsure about is what size radiator I'll need for the CPU, northbridge and two GPUs - they generally come in 1, 2 or 3x120mm, to fit that amount of 120mm fans. I know I'll need more than 120.1 (haha look at me, picking up the notation already..
) but 120.2 and especially 120.3 look like being a very tight fit in the case. I've been having a look at the Thermaltake Armour case and it looks like you'd be able to fit a 120.2 radiator vertically up the front of the case, and possibly put another 120.1 in the loop at the back if absolutely neccesary, as it appears the single fan rads will attach to pretty much any existing 120mm fan mount. I have no idea whether this is possible though, or whether having a huge radiator right in front of the only inlet fans will affect the cooling of the other components.
I need to ask on a few more specialist forums really - have to wait though, as OcUK forums have to approve each membership before you can post there.