If you actually work alot with server stuff you should more look at some home server rig. That mean instead of a way too much overpriced 980x you can get something like that:
Evga sr-2 motherboard why? because its a server motherboard that you can overclock !! isnt that nice ?Cost ? around 600$ will be there around the beginning of the summer.
2x xeon x5630 why? 32nm server quad core cpu and they only cost 600$ each, not too bad and they come with a nice enough 19x multi for overclocking.
As for hard drive and memory, it all depends on your needs, the motherboard if i remember well accept quite all kind of memory. So just buy what you need exactly.
Also go check if any of your server application use cuda core, because if they do, you better get a gtx480 or even 2 cause that will be very helpfull in those apps that can use cuda.
If you dont like my 2xcou build , you can go also for 1xcpu build.
This time because we only have 1 cou, the 980x could be worth its price.
Mobo would be one of the three mobo from Asus supercomputer lineup for lga1366.
If you need pcix, then you need the P6T ws professional, if not then the P6T6 Ws revolution would be my choice because The P6T7 Have 2 nf200 chip and they produce alot of unecessary heat.
The rest is the same thing as the 2xcpu build.
As for liquid cooling, case choice and cooling need are needed to help you choose the right watercooling stuff.
You could go for some 5870 eyefinity cards instead if you were interested in 6-monitor eyefinity. Anyway, I don't know about the PSU. I would be looking at an Antec, Corsair, FSP, Silverstone, Seasonic X-Series, or PC Power & Cooling unit. For a dev build you should have a high quality reliable unit. Anyway, if you're going to be doing development all day I would suggest you set up a subversion server. The subversion server doesn't need to be too speedy, just have a good amount of storage and high reliability. Even if you're not working with anyone else it's good to keep track of changes when working on a large project like a video game.
@snorojr: I've been eying with the XEON stuff, however there are two things I'm missing: currently there's no board which supports USB 3.0 and SATA 3.0 (the Gigabyte does support both), which I specifically looked into for the future. I'd love to have a board ready for dual CPU, but there's currently none feature the two things above (e.g. the Intel Skulltrail D5400XS).
@megamanx00: 6-monitor is not interesting for me, I'll leave it at one for now, maximum of three (if ever), and then I'd use a second 5970 if I get performance problems (but that would be "future", or more specific "far future", anyway)