Drop the MSI board, i would get a Gigabyte DS3 or Asus P5B-E instead. The ram is overkill for your system, this ram will work just as well, and its considerably cheaper. I would get a pair of these instead of the Seagate drives on your list, there a little cheaper an will perform just as well. Might want to get a different gfx card, the 6600LE will work, but its a little under powered, the 7600GS would be a better choice, and its only about $40 more. The psu is also overkill, this one will work fine, and its almost 3 times cheaper.
Agree with many of the suggestions, above. Since you are doing pix and vids, have you considered video capture and larger storage capacity? What are you doing for redundancy of all those files you generate? You'll be happy with the WD HD, along with the good performance already mentioned, they are very quiet drives. IMHO, unless you are gaming, I think you'll be fine with the E6400. If you need a little more juice, it overclocks another gig quite easily. I'd spend the attention and money on storage capacity and redundancy.
I'll be getting two of the 500gb WD drives, and will use my older drives for offline backup. I'll also be moving my dvd writer and dvd player from the old machine, along w kbd mouse and monitor. Gotta save money somewhow...
For video capture (whatever you might mean by that) I either have firewire on the motherboard, or I have a PCI firewire card.
"capture," if you needed to pull off of an S-video or composite video source. Sounds like you're just going directly from device to capture software. You might want to get a card reader for some of your media memory chips, otherwise it looks good. Oh, BTW, I read another post that claims the E6600 is better for your use because of the 4M L2 cache, which video-editing software apparently hogs, irrespective of clock speed.