I certainly wouldn't get the Zalman Water kit, talk about a waste of money.
Building your own at dangerden would be a good idea. Most cases that come with WC have a garbage WC kit, or as someone else said: a water
kit. The same goes for most WC kits. Just custom build it as you do with your computer. It's the same deal really. You could easily build a very effective loop for $200, especially if you get a heatercore.
Just make sure you get blocks that will fit your hardware and fittings that will fit your tubing. That is often a mistake that WC kits will eliminate.
I would go with a heatercore though, unless you plan on spending a fat load waste on an expensive radiator. I just ordered the 1977 Bonneville
heatercore for my loop, can't wait to get it! Heatercores will give a great deal of performance over a radiator. Given their price, it's a deal that can't be beat!
The heatercore I posted above comes pre-modded. You could pick one up at Autozone and mod it yourself, but why bother?