First Build Gaming/Video Rig

Hey all, I found this site through a friend and thought it would be nice to get some feedback. I Haven't played pc games or watched movies on a computer in a long time. I think 2 years to be exact. I've been doing a little bit of research and found some gear I'd like to use for my build but would also love some input on thoughts or suggestions about how it would perform. I don't know exactly how great of a rig I would need to run some of these newer pc games maxed out, but I do know a few games I intend on playing. Crysis I do know is very hardware demanding so I'd like to say I'm building my rig around that game. But I'd like to play Bioshock 1 & 2 whenever that releases, Crysis 1 and Warhead, and Left 4 Dead. I'll probably pick up other games also but I know those I'll end up getting for sure. My monitor supports 1280 x 1024 / 75 Hz max. Hopefully that helps a bit. But heres the rig I'm looking to build.

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
http://www.newegg.com/Product/Prod [...] 6819103471

Mobo- GIGABYTE GA-MA790X-UD4P AM3/AM2+/AM2 AMD 790X ATX AMD Motherboard
http://www.newegg.com/Product/Prod [...] 6813128387

RAM- Mushkin 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Dual Channel Kit Desktop Memory
http://www.newegg.com/Product/Prod [...] 6820146785
Not sure if I would need 8 gigs, at MOST I'd be running a game while burning a dvd and limewire is always open. I don't necessarily plan on doing that but if 4 gigs could tank that I'm straight.

HDD- Seagate Barracuda ES.2 ST3500320NS 500GB 7200 RPM 32MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive
http://www.newegg.com/Product/Prod [...] 6822148294

Video- EVGA 01G-P3-1280-TR GeForce GTX 280 1GB 512-bit GDDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card
http://www.newegg.com/Product/Prod [...] 6814130492

Optical Drive- SAMSUNG Black 22X DVD+R 8X DVD+RW 16X DVD+R DL 22X DVD-R 6X DVD-RW 12X DVD-RAM 16X DVD-ROM 48X CD-R 32X CD-RW 48X CD-ROM 2MB Cache IDE 22X DVD±R DVD Burner with LightScribe
http://www.newegg.com/Product/Prod [...] 6827151176

Case- Antec Nine Hundred Black Steel ATX Mid Tower Computer Case
http://www.newegg.com/Product/Prod [...] 6811129021

PS- Antec EA-750 750W Continuous Power ATX12V version 2.3 SLI Certified CrossFire Ready 80 PLUS Certified Active PFC Power Supply
http://www.newegg.com/Product/Prod [...] 6817371026

OS- Microsoft Windows Vista Home Premium SP1 64-bit for System Builders
http://www.newegg.com/Product/Prod [...] 6832116488

I don't know if I need a better cooling heatsink, I don't plan on overclocking anything. This is my first build and I don't have much of an idea how to access bios or anything if I need to update to run my ram to run at its normal potential. But I'm sure I could google it and figure it out without ruining anything. I do have a friend that could help me put it together but I would like to do it myself. But how do you think that rig would handle games and videos? Thanks, Alan.

Your choices seem ok to me and will do a great job in the games you mentioned at the resolution of your monitor. Shop around and you may save a bit.