1] The RAM is no good, the processor is designed for 1.5v RAM. If you want Corsair RAM then consider the Corsair Vengeance Series which is specifically designed for Sandy Bridge CPU's. Alternatively look at GSkill for quality 1.5v RAM.
The RAM will work but you run the risk of damaging the CPU's memory controller if you use such high voltage RAM.
2] That Motherboard is really not good for a 2500K, I would say that can be like having a Buggatti Veyron engine and no wheels to ride on. The 2500K is designed on the premise for overclocking which that board doesnt give much oc'ing potential. If I were you I would look at a P67 or Z68 chipset motherboard.
PS: Just tell us what kind of budget you are working on so we can come up with some options for you.
CASE: Coolermaster CM 690II Advanced 71.98
The Basic version is 54.95 but doesn't have the external SATA dock to plug in a hard drive out the case, it also doesn't have the GPU rentention brace to reduce the strain on the pci ports by heavy GPU's.
PSU: Coolermaster GX 550w 48.71
I think getting a 850w is seriously overkill for a single GPU system, I use that PSU and run a 2500k and GTX 560TI with plenty to spare, it is 80+ efficient and is more within the "what is needed" bracket with 44A @ +12v
If you are paranoid about power specifications look at the Corsair TX 650.
Motherboard: ASUS P8P67 Pro 119.60
It is a really good for value motherboard and excellent with a 2500K
RAM: Corsair VENGEANCE 1600C9 4GB(2x2) 28.94 or 8GB(2x4) 46.94
The rest you can keep as is.
It will be more expensive but for that target build you can't skimp to much.
This is a great tool for helping you find out how many watts that you need for your power supply http://extreme.outervision.com/psucalculatorlite.jsp . With the Intel® Core™ i5-2500K I would be looking at 750w to give you some overclocking room but if you are going to try to do SLI or Crossfire you may want to look for something in the 850w plus range.
Did the calculator with a 2500K @ 4.5ghz and a GTX 590 and the recommended wattage is 526 excl fans and 12v componants. To my knowledge a 590 needs 49+A to run and nearly 100+ more watts to a 6870. 750w is just going overkill and you will pay through your nose for it. 600-700 is probably safe ground with plenty to spare, while 550-600 is likely to be where you will need a good quality PSU but you will use it properly.