AMD Gaming Machine <$1000

[besaido]

I'm new and I've been looking at lot of posts for the last couple of days.
I want to build my first gaming rig for less than 1000$ that will play future games very well such as SC2, D3 to name a few. Currently I play L4D, WoW, TF2, WC3. I'm not planning to overclock or to use two gpus but do plan on running the two harddrives in raid. I'm missing heat sinks and fans for my list if someone could kindly suggest some.
New egg has a 48 hour deal with a hs
COOLER MASTER RR-CCH-L9U1-GP 92mm Hyper TX2 CPU Cooler - Retail
http://www.newegg.com/Product/Produc...Tpk=35-103-031


Here's my draft of components gathered from a few posts and of my own browsing on Newegg.

PSU - CORSAIR CMPSU-650TX 650W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS Certified Active PFC Compatible with Core i7 Power Supply - Retail
http://www.newegg.com/Product/Produc...82E16817139005

CPU - AMD Phenom II X4 940 Deneb 3.0GHz 4 x 512KB L2 Cache 6MB L3 Cache Socket AM2+ 125W Quad-Core Black Edition Processor - Retail
http://www.newegg.com/Product/Produc...82E16819103471

MOBO - GIGABYTE GA-MA790X-UD4P AM3/AM2+/AM2 AMD 790X ATX AMD Motherboard - Retail
http://www.newegg.com/Product/Produc...82E16813128387

HDD - 2x - Western Digital Caviar Black WD6401AALS 640GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive - OEM
http://www.newegg.com/Product/Produc...82E16822136319

Memory - 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/Produc...82E16820231122

OS - Microsoft Windows Vista Home Premium SP1 32-bit for System Builders - OEM
http://www.newegg.com/Product/Produc...82E16832116485

CASE - COOLER MASTER Storm Scout SGC-2000-KKN1-GP Black Steel / Plastic ATX Mid Tower Computer Case - Retail
http://www.newegg.com/Product/Produc...82E16811119196

I already have a Nvidia gtx 260 vcard waiting for me. My first priority was just trying to make sure everything I chose is compatible hardware wise and space inside the case wise.
Please recommend suggestions to tighten up the components so I don't have wasted space like one post I read was thinking about buying a mobo that can support 3 gfx cards which he wasnt planning on doing.

My PSU could be overkill but I don't know anything about PSU's except for the wattage amount. If I was given choices for PSU's and they could all put out the same amount of wattage, I wouldn't know which one to choose. And it's a toss up for the OS that I want. Vista or XP? 32 or 64bit? Home Pro? Can someone please recommend an OS so I can utilize the most out of my memory and gaming components? I know vista takes alot of ram so you don't actually get the full 4gigs of ram you have for gaming or w/e. I know the 32 and 64 bits help with that but not sure how. 64 bit os allows for more efficient utilization of ram over 4 gigs but I dont think I will go over 4g.