The first impression I got from your configuration was that it doesn't seem to be balanced. A massive case, no SSD, smaller display, not a gaming oriented CPU, ridiculous amount of RAM and a premium version of OS that you wouldn't probably make full use of, are some of the concerns I have. Its just my opinion, so don't take me wrong, you could have a different viewpoint in selecting these components.
I posted a reply in another topic but found it completely fit for your question, so posting it here.
CPU: Intel Core i5 3570K | $229.99
CPU Cooler: COOLER MASTER X6 Elite | $42.99
Motherboard: ASRock Z77 Extreme4 | $134.99
Memory: CORSAIR Vengeance LP 8GB 1600MHz | $57.99
GPU: GIGABYTE GV-N670OC-2GD GeForce GTX 670 2GB | $399.99
SSD: SAMSUNG 830 Series MZ-7PC128D/AM 2.5" 128GB | $149.99
HDD: Western Digital Caviar Black WD2002FAEX 2TB 7200 RPM 64MB Cache | $199.99
ODD: ASUS 24X DVD Burner | $16.99
Case: NZXT Phantom PHAN-001BK Black Steel ATX Full Tower | $119.99
Case additional fan (top): NZXT FS-200RB-BLED 200mm SILENT Blue LED Fan | $19.99
PSU: SeaSonic X Series X-850 (SS-850KM Active PFC F3) 850W 80 PLUS GOLD Full Modular | $199.99
Monitor: ASUS VE278Q Black 27" 1920x1080 2ms Full HD HDMI LED | $319.99
Mouse: RAZER Naga Molten RZ01-00280500-R3M1 USB Wired Laser 5600 dpi Gaming Mouse | $68.99
Keyboard: Microsoft SIDEWINDER X4 | $47.99
OS: Microsoft Windows 7 Home Premium SP1 64-bit | $99.99
You have very good points, but the CPU (when over clocked) will be outstanding for hosting server's and playing BF3 and other games (i will need alot of ram to get full power from both cross fired GPU and to run BF3 on ultra) . I have 4 other screens those exact model and size, the case if when (yes when) i expand my hard drives, i only am using one the start off with because i am waiting till SSD's become much cheaper and bigger. But ill look into the Optical drive you have suggested.
I honestly would get an FX-8120 if you insist on an FX CPU. Its the same as the 8150, and its cheaper, just overclock the 8120 to 3.6GHZ and you have yourself an 8150. There is no real advantage in terms of how much further you can overclock an 8150 over an 8120. So, its just not worth the additional cost.
The cross-hair formula mobos are stupid overpriced. If you want a super fancy board, consider an Asus Sabertooth 990FX. Its cheaper than the Crosshairs, and has a better warranty.
If you plan on really overclocking the crap out of an FX-8120/8150 with two 7950s in crossfire, I absolutely would not touch anything below 750 watts. Yes you could probably get away with 600, but I also have a friend who used a 20oz mountain dew bottle as his antifreeze reservoir on his acura integra, doesn't mean its a good idea lol.
All of the PSUs Loon suggested to you are good. The corsair TX750 he recommended to you is the one I have. I recommended the TX850, either should work for your purposes.
I think I'll get the H100 instead of the CPU fan cooler, I could make a custom water cooling unit but a cant be stuffed to (even thou it's moderately easy) would the H100 fit inside the cosmos 2 case because I have read reviews that state the H100 doesn't fit properly in a "push pull" configuration. But I might just stick to a pull configuration with the rad on the top attached to 2 of the 3 top fans. Would you guys recommend this?
I would advise against water cooling unless you know what you're getting into. But the H100 is a good water cooler. I don't know if it fits in a Cosmos II, but I can definitely say it would fit in an NZXT Phantom if that helps. Although if you want big cooling, consider something like a Noctua D14. Watercooling is a lot less necessary these days and still as dangerous as it ever was.
As far as power usage with hard drives, a standard hard drive uses about 10 watts under load nowadays. Now realistically, you'd probably never be using all 6 at once, but I'd still factor in 10 watts per drive. Figure in 20 watts (just to be on the safe side) for an H100.
750 watts is plenty, but the 850 model gives you assurance, and it wont hurt to have more than you need. A good PSU can last you 10 years easy. Corsair TX series are Seasonic made and very good.