Photo Editing System Build

I would recommend:
Quad, some photoediting software utilize multiprocessors.
- At this time, the DDR3, is not worth it as the prices are high. If you plan to OC then the DDR2 can beat the lower end DDR3 no problem.
-GPU is based on preference. Using only 2D, you won't gain any performance on DDR5 and crossfire/SLI. The 4850 should be more than enough for your needs
-Mainboard is based on preference. Coming from a Gigabyte user, I am currently using the Asus. Both of them are solid boards.
- I would recommend you use mirror only for your data. You should get 1 more HDD for the OS. Dont forget that you OS is constantly writing data on your HDD, If you mirror your HDD, you are putting a lot of strain read/write onto your HDD. To be honest, I dont see any reason for Mirroring. You might be better off with doing constant backups rather than Mirror.
-Ditch the PSU.. Rosewill isn't a quality PSU. I would recommend Corsair 620HX - its solid and one of the best PSU.

This is what I would go for:
Q9450 OC to Q9550
-OCZ 8 GB DDR 800
-ATI 4850
- PSU Corsair
Board either Asus or Gigabyte (some Asus boards have some ram compatibility with OCZ, so if you plan to get Asus Boards, you might want to check other brands)

Thanks for your suggestions guys! I really appreciate the input!

I'm settled on Q9550 (Q9450 is practically the same price, and out of stock). In your opinion, how much can I safely overclock this beast to, while maintaining stability and longevity with air cooling? I'm sure I can easily hit 3Ghz even with stock HSF. Now I'm not much of an OC guy, but by boosting FSB I will indeed be OC'ing the RAM as well correct? I'd like to get DDR2 to at least 1066, maybe more as long as heat is not an issue (I'll have 4 tightly squeezed sticks on the mb).

For the MB I like how the UD3R looks, however I think I should aim at something with an X48 chip. I like the Asus Rampage. However, the DDR2 version of that MB lacks esata, which seems pretty important for my use (I use quite a bit of external drives, and USB2 is just tooooo slow). Let me know what your suggestions are. Like I said, for a $300 CPU I don't mind shelling out 2-300 for a MB to avoid any kind of a bottleneck.

For RAM I like the idea of sticking to DDR2 for now....will primarily go based on whats a good deal and reviews (mushkin if its not out of reach). Any specifics I should look for? 800, 1066, 1200? good latencies? 5-5-5-12? Cooling? Open for ideas here

GPU Will NVidia and Intel make a better fit than ATI or is that totally false? Considering the occasional gaming/graphical applications, I'd like a capable system. GDDR5 cards are not that expensive. I like the 4870 chip with GDDR5 memory, a 1GB card costs 299. Would it be wiser to get a GDDR3 card with 2GB? What will give me better performance IYO? The card will run at 1920X1200, so I need something pretty capable.

I originally was pretty set on MC Centurion 5, because of size, design, and capability. I like the front, full-face filter that you can vacuum up as dust accumulates...a lot simpler than taking the whole thing apart to vacuum! I built a few of these for friends, and after a few months, the insides still sparkled! However the Antec 300 (900 is too big) is actually pretty decent, probably even better than the MC. It works even better because its a tad smaller than the Centurion 5, so a plus there. Will the 500W PSU be sufficient for my needs? (3X sata drives, posibly crossfire in the future, 4 sticks ram...) It looks like a good deal with the 550W PSU. The sonata III case also is appealing due to size, but it laks front filters and has that annoying lockable drivebay cover.

Monitor: I'm narrowing in on a purchase of an S-PVA panel, but not quite there yet. Biggest contender is the Samsung 245T or its predecesor 244T. Both are identical panels and a couple of hundred $ apart. It looks like a really good deal, and perfect for photo-editing. Has anyone played any fast games on it to notice any ghosting/lag??? Hopefully it performs well given its acclaimed 6ms g2g response.

Thanks to all for your suggestions again. Can't wait to power this beast up....and use it to calculate pi to 1 millionth of a dec. place !!