Unless you have a fair bit of cash to burn, custom water-cooling isn't for you. $300 is what I would consider about right for an easily upgradable CPU loop, with each GPU after that about $150 to add in.
However it offers the best performance you will see until you start using Liquid Nitrogen or start chilling the water, the most flexibility in what you can do and if you do it right, a very silent rig. It is fairly complex, but that's why resources like the water-cooling sticky exist.http://www.tomshardware.com/forum/277130-29-read-first-watercooling-sticky
That EK kit is a custom loop, you just get everything you need in the one box. Kit options are a fairly easy way to get into a custom water-cooling (I started with an XSPC RS360 kit) but can limit you later on if you get a cheap one (pump mainly).
Your CLC (Closed Loop Cooler) options like the Corsair Hydro series, they perform similarly to equivalent air-coolers for about $20-30 more. That H60 is about equal to a 212 EVO, the H100i is about equal to a Noctua NH-D14 in terms of cooling performance. Its really not worth getting over an air heatsink unless your looking into the 240mm rad options or some other requirement (small case, constant travel, RAM height, etc) dictates.