Is the mother board good enough for high oc's and will it go good with the memory?
Is the power supply good enough if I decide to go SLI on a pair of gtx's 570?
Should I spend Alot more money on a SSD or stick with this regular drive?
Is the water cooling good enough ?
Almost all the new P67 motherboards are good, and will OC to sane levels equally well. Pick one based on features you want. I think the ASUS is good, they seem to have been at it a bit longer than most, so most bios issues will have been worked out. The vengeance ram should be good with sandy bridge. Check the corsair configurator or the mobo qvl list to be certain.
The psu is a good one. With 62a, it might even be good enough for two GTX580's. Unless you are gaming at 2560 x 1600, or plan on triple surround gaming monitors, a single GTX580 would be excellent. By the time you need an upgrade, there will be better cards around, and a GTX580 will still have good value as a top single gpu card. A single card avoids issues with games that do not play well with dual cards.
Very few games can use more than 2, let alone 4 cores, so the hyperthreading capabilities of the 2600K will go largely unused. Don't know how to measure the extra L3 cache value.
A 2500K will likely OC to the same levels. If you are on a budget, get the 2500K, It will drive anything well. If the extra $100 is not a problem, get the 2600K.
I would plan on a SSD in a month or so. Gen3 SSD's are due out, and they will be faster and cheaper. In the mean time put your OS and apps on a 80gb partition on the hard drive, planning on cloning it to a ssd later.
The water cooling is not necessary. Any decent oem cooler will do the job, and be simpler and cheaper.
Sandy Bridge overclocking no longer involves the B-clock any more, so multiplier overclocking is the way to go. Pretty much any mainboard from a quality manufacturer will do. Asus certainly qualifies.
Instead of that multi-rail power supply, I would suggest something with a single large 12v rail.
Reviewers have been getting up to 4.5GHz overclocks with the retail box heatsink, so liquid cooling isn't necessary. A good air cooler will suffice.
I'm going to be getting a (mostly) new machine with my tax refund money as soon as it's direct-deposited. It's something similar to yours:
Cooler Master Hyper 212 Plus (extremely good cooling for only $30)
Asus P8P67 (just the basic one; don't need the fancy-schmancy crap)
G.Skill Ripjaws X Series 8GB DDR3 1333 (or 1600; haven't decided for sure yet)
Palit GTX 570 Sonic Platinum (factory OC'd to 800/1600/4000)
WD Caviar Black 1TB 6GB/s
Cooler Master HAF 912
Cooler Master Blade Master 120mm case fan (five extra - one as a second fan on the heat sink, and four to fill the extra spots in the case)
Cooler Master GX Series RS750 power supply