Help a newbie choose a Graphic Card!

I have an Apple 20" Cinema Display. Play loads of games like COD4, COD5, Far Cry, Crysis, etc... (Mostly FPS games...) Also a library of music, movies, raw photos, video encoding.

What would be a good graphics card for my uses & are my components good enough as below ?

Items to buy:

1.. JM800QLU-2G Transcend® JetRam™ High-Performance 2GB DDR2-800 240-Pin Module : CL5, 4-Layer PC Board, Life-Time Warranty
2. GZ-X1-360W Gigabyte® X1 Chassis - Black - Side Vented Panel - 4x 5.25" & 6x 3.5" Bays - Tool Free Design - 1x 120mm Fan - 360W PSU
3. BX80570E8400 E8400 Intel® Boxed Core2™Duo E8400 Processor - 3.00GHz Dual Core, Socket 775, 6MB, 1333MHz FSB, 45nm, x64 Support, 3 Year
4. 7. GA-G31M-S2L DUAL DDR2-800 GIGABYTE® "S Series" G31 & ICH7 Express Chipset - Socket LGA775 @ FSB1333 - For Celeron®D, Pentium®D & Core™2 Series S Series 3 YEAR WARRANTY 1x PCI Express x16, 1x PCI Express x1, 2x PCI, 2x DDR2-800 (Dual), 4x SATA2, 1x ATA100, 8x USB 2.0, Realtek 10/100 LAN 5.1 Channel High Definition Audio, Features Gigabyte SMART & SAFE Technology, Vista Premium Certified
5. Seagate® Barracuda™ 7200.11 Series - 320GB Serial ATA II (SATA2) Plus - Serial ATA 300 (3Gbps), With 16MB Cache @ 7200RPM - NCQ - ST3320613AS
6. DH-20A3S SATA LITEON® DVD Super All-Write SATA, 20x+R/-R, 8x +R/-R DL, 8x +RW, 6x -RW, 12x -RAM, 16x DVD, 48xCDR, 24x RW, White & Black

My options for my graphics card are as follows:

1. Leadtek NVIDIA® GeForce 9800GT, 512MB 256Bit DDR3, PCI-E 2.0, Dual DVI, HDTV, DirectX 10, OpenGL 2.1, SLI Ready, Vista Premium
2. Gigabyte® NVIDIA® GeForce 9600GT, 512MB 256Bit GDDR3, PCI-E 2.0, Dual DVI, HDTV, DirectX 10, OpenGL 2.1, SLI Ready, Vista Premium
3. Gigabyte® ATI® Radeon HD3850, 256MB 256Bit GDDR3, PCI-E 2.0, Dual DVI & TV-Out, DirectX 10.1, OpenGL 2.0, Shader Model 4
4. Gigabyte® ATI® Radeon HD4850, 512MB 256Bit GDDR3, PCI-E 2.0, Dual DVI & TV-Out, DirectX 10.1, OpenGL 2.1, Shader Model 4.1, Crossfire

* Notes:

1. I think i need to get a larger PSU like maybe a 460W or something...

what do your think ?

For a 20" monitor, I would go for a 4870 with 1 gig of memory, or even if money is not a concern, a 4870X2.
Definetly though, at least the 4850.
You will need a much better PSU no matter what you do.
Check reviews and buy a good one. A few extra spent here is worth a ton later down the road.