First, you may want to browse the hardware/software forum going back at least a few months since this topic recurs every month at least...
Off the top of my head, assuming from your RAID statement that you have excess cash to burn...
ASUS A8N SLI Premium. Also available is the Deluxe for $10 less.
http://www.newegg.com/Product/Product.asp?Item=N82E168131315402 gig GSkill memory (2x1 gig). This is what I currently have and it works fine, but I haven't tried overclocking it.
http://www.newegg.com/Product/Product.asp?Item=N82E16820231032Athlon 64 3700+ $212ish Again, this is what I have because it's right at the price/performance elbow where any faster and you get huge price increases for marginal speed increases.
http://www.newegg.com/Product/Product.asp?Item=N82E16819103539Or if you want dual core, Opteron 165 and overclock it, $325.
http://www.newegg.com/Product/Product.asp?Item=N82E16819103588If you want you can spend more on the cpu, but I wouldn't at this point. Wait a bit and prices always drop.
Video card - 1 or 2 Nvidia 7900 GT ($299 but currently out of stock at newegg) or 7900 GTX 512 meg, $499 but currently out of stock at newegg.
Hard drive - 2 of the new updated WD raptors, 10k rpm and 150 gig each
http://www.newegg.com/Product/Product.asp?Item=N82E16822136012Sound card - soundblaster X-Fi, any variety
Any dual layer DVD burner. I have a sony and it works fine but because of their rootkit intrusion and complete lack of real remorse (I was a victim and had to reinstall windows to kill it), I will never recommend any sony products to anyone again. Sony are teh evil, and there are MANY drives out there that are both faster and cheaper.
500 watt minimum power supply... If your case came with one less than 500 watt, consider tossing it out or you may spend weeks chasing down random system glitches especially if you go with RAID raptors and SLI vid cards.
Monitor - The Dell 1905FP LCD is on sale for under $300 now. This was the LCD standard for nearly 1.5 years and only 4-5 months ago cost over $450. It's aging a bit but still good enough that I just ordered one yesterday. I have a crappy NEC LCD that's probably defective and although it's rated at 25ms response time, I've never noticed ghosting so I'm sure I'll be happy with the 19" dell when it arrives.
That ought to get you started. Ways to cut costs without sacrificing too much speed is to get only one 7900GT and get a single regular hard drive. Those raptors cost around $300 each but you can get a 300+ gig 7200 rpm drive that is "fast enough" for under $150. You can save a little money initially on the sound card too since those ASUS boards have decent onboard sound, but YMMV with the quality. Some find them acceptable, some don't. The soundblaster X-Fi cards will reduce cpu usage by a few percent and if you don't install all the bundled software, they're actually decent to use.