Now before I get into this, this was actually harder than I thought since we're starting completely from scratch and I didn't want to skimp on some parts, on other areas I did. Now I went with a quad core since you said you did some Photoshopping and movie editing. The quads will clock slower than their dual core brothers (at the same price point), but will shine more in multimedia applications than games. If you're more serious in gaming, I'd opt for the faster clock speeds of the dual cores as they do better for games for the money.
To keep the price down, I skimped on the case/accessories rather than the guts of the PC. A lot of the parts I selected I went with the best rating customers offered on Newegg, rather than researching benchmarks or official reviews (for time reasons).
Alas, I'm eager to see what other people post with their setups. There are a lot of options out there, so remember there can be several brands/models of a part that you can interchange w/ anyone's recommendaiton. Anyways, here's what I did in about 30 minutes.
Intel Core 2 Quad Q9300 Yorkfield 2.5GHz LGA 775 95W Quad-Core Processor Model BX80580Q9300 - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115043$249.99
ASUS P5Q Pro LGA 775 Intel P45 ATX Intel Motherboard - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131299$119.99 - $15 MIR = $104.99
SAPPHIRE 100242L Radeon HD 4850 512MB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102747$164.99 - $20 MIR = $144.99
G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory Model F2-6400CL5D-4GBPQ - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E16820231122$54.99
Seagate Barracuda 7200.11 ST3500320AS 500GB 7200 RPM SATA 3.0Gb/s Hard Drive - OEM
http://www.newegg.com/Product/Product.aspx?Item=N82E16822148288$69.99
Creative Sound Blaster X-Fi XtremeGamer 7.1 Channels PCI Interface Sound Card - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E16829102006$85.99
LITE-ON 20X DVD±R DVD Burner Black IDE Model DH-20A4P-04 - OEM
http://www.newegg.com/Product/Product.aspx?Item=N82E16827106228$21.99
Acer P243WAid Black-Silver 24" 2ms(GTG) HDMI Widescreen LCD Monitor with HDCP Support - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E16824009125$339.99
PC Power & Cooling S61EPS 610W Continuous @ 40°C EPS12V SLI Certified CrossFire Ready 80 PLUS Certified Active PFC Power Supply - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E16817703005$109.99 - $30 MIR = $79.99
Logitech 967738-0403 Black USB Standard Deluxe 250 Keyboard - OEM
http://www.newegg.com/Product/Product.aspx?Item=N82E16823126013$6.99
Logitech SBF-96 Black 3 Buttons 1 x Wheel USB Wired Optical Mouse - OEM
http://www.newegg.com/Product/Product.aspx?Item=N82E16826104026$8.25
GIGABYTE GZ-X5BPD-500 Black SECC Steel / ABS ATX Mid Tower Computer Case - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E16811233039$34.99
Microsoft Windows XP Home Edition SP3 English for System Builders 1 Pack CD - OEM
http://www.newegg.com/Product/Product.aspx?Item=N82E16832116511$89.99
TOTAL BEFORE REBATES: $1,358.13 (NO S/H)
TOTAL AFTER REBATES: $1,293.13 (-$65)
AVG S/H: $50-60?
TRACK IR 4 w/ CLIP: +$150 (NO S/H)