Intel's performance ratings really do not make up for the prices they charge. AMD is a better bang for your buck when it comes to processors.
Unagi, why don't you scope out NewEgg and compile a wish list of your build? You shouldn't have any issues whatsoever building what you've listed for far under $1,000! I'd be looking for at least 16GB of RAM though, especially if video and audio editing is high on your priority list. You could keep it cheap and stick it out with DDR2, or jump on the bandwagon with DDR3 and future-proof yourself. It's up to you. Most motherboards will let you jump up from DDR2 to DDR3 later anyway.
You shouldn't need to worry about RAID. You can get single 2TB drives super cheap nowadays. I always preferred a simple Master/Slave setup to RAID anyway.
AMD has some great AM3 socket processors that can be acquired on a modest budget. The Phenom II quad core lineup even comes in nifty "Black Editions" for easy overclocking if need be.
Find a good nVidia GPU. 1GB dedicated memory shouldn't be difficult to keep in the budget, as it's pretty much the standard now.
Get a good motherboard!!!. I almost always prefer Asus as a starting point, but have also been impressed with Gigabyte. I'd hazard against the no-name brands, and definitely stay away from "gamer" junk like BioStar... they may look pretty, but they're crap out on you eventually.