You failed to mention the most important element: Your software.
For example, if you are going to use Adobe Premiere Pro, there are some specific hardware requirements. This goes even further if you will add a graphics/editing effect accelerator, like the RT.X2 The editing accelerator really will reduce editing time and give you more "real time" effects.
Basically, don't figure on a lot of advantage going to a RAID array. It's more important just to have fast hard drives and put the OS on HDD 1 and use HDD 2 for scratch edits and export to HDD 3.
Consider Matrox Graphics cards for dual or even triple monitors. It's very convenient and no doubt cheaper to use two 20" or larger monitors than one of the larger, 24, 26 or 28" monitors. You end up with more real estate on your desktop, too. The P750 is a good video editing card. (But doesn't "qualify" for use with RT.X2 hardware accelerator.)
I think most of today's systems will accommodate video editing very well. Double check over at
Motherboards.orgI would also skip the "Extreme CPU." You don't really need it. Spend your money on RAM, a Lian-Li aluminum case, extra fans and an Enermax high-end power supply. Separate SATA HDD drives are essential.
Avoid problems: Check with your video editing software manufacturer (like Adobe, etc.) to determine which motherboards and chipsets will work best with their products. In the end, video editing is somewhat less about speed and somewhat more about compatibility. If you get a hardware accelerator, it is absolutely essential.