Updated First Build. Please Help. Thanks.

Hello, below is my new updated build thanks to everyone whose been so helpful here. Please give me any last thoughts/changes I should consider. This is my first build so I don't know much. The rig is mainly going to be used as a graphic workstation and gaming. I've never overclocked before, but it's something I'd like to try if it'll better the performance of this build. The total comes to $670 including tax + shipping. I'd really like to get this down if at all possible to around $600. If anyone has any suggestions, that'd be great. I'd also consider switching to AMD if that'll make it cheaper. Here's the build. Thanks again for all the help thus far...

case: COOLER MASTER Centurion 534 RC-534-KKN2-GP = $49.99
http://www.newegg.com/Product/Prod [...] 6811119106

cpu + mobo (combo): GIGABYTE GA-EP43-DS3LR + Intel Pentium E5400 Wolfdale 2.7GHz = $159.98
http://www.newegg.com/Product/Comb [...] mbo.181203

cpu cooler: XIGMATEK Dark Knight-S1283V = $39.99
http://www.newegg.com/Product/Prod [...] 6835233029

video: XFX GS250XYDFC GeForce GTS 250 512MB = $129.99 (is it worth spending $15 more on the 1 GB version?)
http://www.newegg.com/Product/Prod [...] 6814150357

psu: OCZ StealthXStream OCZ500SXS 500W = $59.99 ($10 rebate)
http://www.newegg.com/Product/Prod [...] 6817341012

hdd: Western Digital Caviar Black WD6401AALS 640GB = $74.99
http://www.newegg.com/Product/Prod [...] 6822136319

memory: G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 = $42.99 (will this work on the mobo I chose?) http://www.newegg.com/Product/Prod [...] 6820231122

cd/dvd: LG Black 22X (CAV) = $24.99
http://www.newegg.com/Product/Prod [...] 6827136152

fan: MASSCOOL FD12025S1L3/4 120mm Case Fan = $4.99
http://www.newegg.com/Product/Prod [...] 6835150070

The Total of the AMD 720be would be at $640 without a heatsink and youll need one with OC'ing.

Heres my Specs using your psu/gpu/optical:
http://www.newegg.com/Product/Prod [...] 6822136319
wd black 640gb

http://www.newegg.com/Product/Prod [...] 6820231209
pi black 2x2gb

http://www.newegg.com/Product/Prod [...] 6819103649
amd 720be

http://www.newegg.com/Product/Prod [...] 6813131340
asus 770 atx

http://www.newegg.com/Product/Prod [...] 6811119137
rc-690

http://www.newegg.com/Product/Prod [...] 6817341012
ocz 500w

http://www.newegg.com/Product/Prod [...] 6814150357
gts 250 - see why your getting it cod wow for free, im getting the gtx 285 to get it for free .

http://www.newegg.com/Product/Prod [...] 6827136152
lg x22 dvd

now thats at $640 without shipping and without any rebates.

adding the s1283v will bring it up to the price of the intel build you built. and you will need one of those if you OC.

http://www.newegg.com/Product/Prod [...] 6813131362
asus

http://www.newegg.com/Product/Prod [...] ntec%20300