-ASUS MAXIMUS IV EXTREME LGA 1155 Rebublic of Gamers Intel P67 DDR3 2400 ATX Motherboard - Asus OR Asus Rampage III Extreme Socket 1366/ Intel X58/ 3-Way SLI & CrossFireX/ SATA3&USB3.0/ WiFi/ A&GbE Motherboard by Asus ?
On the motherboard, I would get a more modern z68 chipset. Just look for basically the same ASUS board features in socket 1155 and z68 chip set.
For the CPU the Core i7 2600k is a good choice. You need the k model for over clock.
Ram get dual channel DDR3 1600 8gb(2x4gb Kit). Triple channel is for older Socket 1366 CPU.
Graphics card - According to Tom's and other sites, the 6990 and 590 cards are about the same. Keep in mind though, that the new AMD 79xx series cards are about to be released.
For the power supply, the Coolermaster gold series is probably as good as any, although you might save some money looking at Antec, Corsair, Seasonic, even in the Bronze series. I have a Coolermaster Bronze series 450w in my HTPC and it is very quiet and stable.
I have never done water cooling, but I hear the Corsair products are quite good.
The rest looks fine, and no to the LGA 2011. Most reports state it will be minor improvement over Sandy Bridge.
Ok.. you have an enthusiast budget here, the thing is what games are you playing, and how many monitors do you plan on using?. If you are using 1, then just go for a i5 2500k , a z68 mobo, a gtx 590 and 8 gigs of ram. No need to Spend more. But if you are going for 3 monitors, then get 2 gtx 580 an i7 2600k a evga ftw series motherboard and a 1200 watts psu.