First gaming system in 4 years need value advice

Hi all,
First, thanks in advance for any input you all may provide; this is a great resource. So, I want to build a sub $2000 gaming system that will also do well with Photoshop and Painter X. I have selected the components below and would appreciate any feedback as far as switching out components for better value. Note: I dont plan to crossfire, so I selected a 4870 x2 which should run through the PCIe 2.0 x16 slot on the P45 motherboard below. This should avoid the bump down to x8 seeing as how I'm not crossfiring two physical video cards right? Also, I have never overclocked, but would like to get the q9550 up to about 3.4GHz, can this build handle it with a CoolerMaster Hyper TX2 fan? Is the PSU good enough? Anything I missed? Thanks again!

1 LG 22X DVD±R DVD Burner with LightScribe Black SATA Model GH22LS30 - OEM - $31.99

1 COOLER MASTER COSMOS 1000 RC-1000-KSN1-GP Black/ Silver Steel ATX Full Tower Computer Case - Retail - $199.99

2 HITACHI Deskstar P7K500 HDP725050GLA360 (0A35415) 500GB 7200 RPM SATA 3.0Gb/s Hard Drive - OEM - $129.98

1 SAPPHIRE 100251SR Radeon HD 4870 X2 2GB 512-bit (256-bit x 2) GDDR5 PCI Express 2.0 x16 HDCP Ready - $549.99

1 APEVIA WARLOCK POWER ATX-WA750W 750W ATX12V / EPS12V SLI Ready CrossFire Ready Power Supply - $139.99

1 OCZ Gold 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Dual Channel Kit Desktop Memory - $219.99

1 GIGABYTE GA-EP45T-DS3R LGA 775 Intel P45 ATX Intel Motherboard - $159.99

1 Intel Core 2 Quad Q9550 Yorkfield 2.83GHz LGA 775 95W Quad-Core Processor Model BX80569Q9550 - $324.99

The first thing I would change is the Hitachi drives. The WD 6400AAKS is pretty much the fastest HD for the money.

Western Digital Caviar SE16 WD6400AAKS 640GB 7200 RPM 16MB Cache SATA 3.0Gb/s Hard Drive - OEM
http://www.newegg.com/Product/Prod [...] 6822136218 $79.99

I would also go with a better brand of PSU. It's pretty hard to beat the value of this Corsair:

CORSAIR CMPSU-750TX 750W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS Certified Active PFC Power Supply - Retail
http://www.newegg.com/Product/Prod [...] 6817139006 $129.99 -$20.00 MIR

Do you really want to go with DDR3? You could save some money by going with:

GIGABYTE GA-EP45-DS3R LGA 775 Intel P45 ATX Intel Motherboard - Retail
http://www.newegg.com/Product/Prod [...] 6813128344 $126.99 -$20.00 MIR

mushkin 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory - Retail
http://www.newegg.com/Product/Prod [...] 6820146731 $82.99 -$20.00 MIR

The DDR2 800 RAM will allow you to get the Q9550 to 3.4GHz since it has an 8.5 multiplier - 8.5 * 400 = 3.4GHz.

Edit: Zenthar's response came in while I was typing this up, but we came to a similar result!

The above posters are correct in suggesting Western Digital HDDs and DDR2. Also, research your PSU carefully, make sure it works as intended with your chosen configuration...including conenctors and 12v rail amperages.

I will suggest ignoring OC'ing and any components specifically chosen for OC'ing, your improvements will be minimal in visual end results. Only in benchmarks and very specific borderline-underpowered circumstances will you get performance advantages.

If you wish to do it for kicks and learning, by all means!