This PC setup looks really nice, even more than ehough to run WoW with ultra settings. But IMO points that should be noted:
1. WoW as 32bit application simply can't use more than 2Gb of RAM. Even if WoW developers are smart enough (for sure they are
) and compile it with /LARGEADDRESSAWARE flag - the cap for mem usage is only 4Gb. So it's enough to have 4Gb RAM if the PC is "WoW-only".
2. Liquid cooling is great, but in needs more attention than classic air coolers. Every year or so the liquid have to be replaced to keep all the system clean. Also these systems often can be even more noisy because it has not only fans, but also water pump, which is far from beeing noiseless.
3. The one thing that I'd suggest adding is SSD drive. Any of latest models is OK, for example OCZ VERTEX 3 based on SandForce SF-2000 family flash memory controller. The exact model is not so important, just make sure it's over 80Gb capacity. SSD makes both Windows and WoW run smoothly without freezes and also speeds up any kind of loading/zoning/phasing processes.