Make sure to choose the 2600K cpu for overclocking (with your 5D files you want to)
I like the Asus P8Z68 V PRO mobo for the 1 button overclock and the many sata connections for your disks (look at PPBM5 benchmarks how many Asus mobo's)
Skip the SSD's $$$ and no gain for your Pre pro editting machine.
1HD (Samsung F3 or F4 7200 rpm) for windows and your programs
1 to 4 HD's (Hitachi 7K3000 serie, 1.5/2/3 TB) for the 5D files, if using only 5D file 1 HD will do fine.
2 HD's (Samsung F4 / F3) in raid 0 for cache/ preview
! HD for output (any type)
At least 750 watt PSU,
I just build one my self and it's very, very well for € 1250,- ( also like my Fractal design, Define 3 case, low noise 8 disk case)
I really cannot recommend any OCZ or any Sandforce-based SSD for your new editing build: These SSDs have been a bit unstable when just running Windows, with their random BSOD (Blue Screen of Death) issues. In addition, several people found that the Sandforce SSDs degrade seriously in performance with use (as reported by Harm Millard) - and this degradation is serious enough to require a complete secure erase and a complete reinstallation of the OS just to restore their performance. (You might not notice it after one day, but this degradation takes place over a period of several months or even a couple of weeks.)
In addition, without knowing which line of PSU, it is likely that the Cooler Master PSU that came with that case is one of their lesser models, being unable to provide anywhere near its full "700W" advertised rating without exploding.
Third, I would have purchased the "K" version of the i7-2600, as the plain i7-2600 is only "limited unlocked": Only the single-core Turbo multiplier can be set on such limited unlocked CPUs. In this case, the maximum multiplier (with only one core in use) can be set to up to 42x - and then, the multipliers for multi-core usage cannot be set independently of the single-core multiplier. Instead, the multi-core multipliers get increased above their stock values by the same number of steps as the single-core multiplier (for the i7-2600, at its maximum single-core multiplier of 42x, the maximum overclocked clock speed would be 4.2GHz with one core, 4.1GHz with two cores, 4.0GHz with three cores or 3.9GHz with all four cores).
I agree with the above recommendations.
If you want to get the best bang for the buck ($2000), then loose the SSDs. Get a speedy F3 or F4 instead.
Get the 2600K version of the CPU so you can overclock now, or down the road. Your 5D H.264 footage is CPU hungry, so the more CPU power you have, the better.
Get a gold standard PSU.
Hitachi 7K3000 hard drives are a good choice. You won't get a bottleneck with dual stream H.264 off a single drive, so one for the media (non-RAID) is fine. Just make sure, as mentioned above, to separate the different tasks to different drives (media, cache, previews, export). Or parity RAID them together for security (RAID5 or 3). But don't use the onboard RAID5 controller. Get an PCIe card.