It looks like you really did your homework. I have built quite a few machines and at the have my newest built, my video system. I have a graphic system for Adobe CS & Dreamweaver MX using Win 2000. The other machine is my Linux w/ Fedora Core 4. The last but not least, is my little Dell 600M, loaded with the ability to do video+, maximumized to the T's. The first 3 were built by me and all upgrades on the 600M was my doing.
Just checkout my rig. This is my dream machine. I upgraded from my older version this month, spending about $1000 on eBay. The PCI-E card was more than what was needed. Since I'm not an extreme gamer, the AGP card is more than what's needed for video editing. What I really need is Edius Pro for ultimate editing.
I believe RAM and more RAM is necessary. Get SATA drives forever. Have fun, I did.