koolance.com for your cooling system. I made mine from them and everything was awesome.
newegg.com for your compluter parts. pick a 2011 socket motherboard, your choice processor, choice graphics card, any ddr3 ram at or over 4gb in size, blu ray drive, power supply, hard drive, and operating system.
I doubt the gtx 680 has a water cooling block for it yet, but koolance would have one if there is.