WoW really doesn't need a very powerful system to run at full quality so having a system with a 6-core in it is just overkill.
Also don't get hung up over "liquid cooling" because that's just a marketing ploy aimed at people with limited tech knowledge - it's going to be one of those self-contained units like the CoolIt Domino or Corsair H50, which frankly aren't all that good, but the specs don't even say what the cooler is.
Personally I'd not get any of these systems. The core spec on paper is fine, but they seem expensive and I just know they'll be cutting corners with the power supply and possibly the motherboard.
Building yourself is really easy, especially if the regulars here help you through it, but if you don't fancy building yourself then I'd suggest going to a more local PC builder and talking to them to get a more customised spec.
I'm running a dedicated WoW box downstairs with the following spec:
AMD Phenom II X2 550 Black Edition
Asus M4A785D-M PRO AM3 motherboard
4GB Patriot Sector 5 Viper II 1600MHz DDR3 RAM
ATI Radeon 5770 graphics card
Corsair CX400 PSU
Samsung SpinPoint F3 500GB hard drive
Antec Mini P180 case
Even using the stock cooler for the CPU it's whisper quiet and has plenty enough grunt to run WoW full settings at 1920x1080 resolution on my 50" plasma TV.
That system will cost about half of the ones you've listed and would probably be more robust too.