One question i have is, this motherboard is currently out of stock. is there one thats similar that i can get that will still work with the rest of my setup?
also should a get a duo or quad core processor? i know games run better on duo but would a quad make the computer faster overall? or is it just a waste?
Good choice for the graphics card. In your case, using photoshop and the like, a quad core may not be a bad idea. The Quad might not show the high performance of the E8400, but I think you will be able to use the extra cores. The mobo is a good one, I have one thats very similar. You might actually want to check giga-byte.com to see that the BIOS on that mobo will work out of the box with the E8400.
Unless you plan on overclocking the E8400 past 4 GHz, DDR2 800 is all you need. The motherboard states it will accept up to DDR2 1200 but that means that DDR2 1200 is the maximum the board can support without overclocking. All boards are backwards compatible with lower clock memory.