Need help on buying a new graphic card!!

hey guys, am new on buying a new graphic card and i wonder if you can help me, am looking for a graphic card that is good for gaming, and i got 2 in mind, but its difficult to decide when your new at this.. am either getting

XFX Radeon HD 4890 Video Card - 1024MB DDR5, PCI Express 2.0 x16, CrossFireX Ready, (Dual Link) Dual DVI, HDTV

or a ..

EVGA nVidia GeForce GTX 280 1 GB 01G-P3-1280-AR

the radeon is a bit cheaper, but the price is not my concern, the performance is, becuase i want a graphic card that would be good in gaming, and i also want to know the difference between Nividia and Radeon, Is Radeon not compatible with some games such as unreal tournament or COD MWF2? i checked on the top ten best graphic cards for gaming and the radeon ranks on 5 yet the Nividia GTX 280 ranks on 6 or 7 but i dont really trust it, and since you guys are experts at this i want your opinion please give me as much details and information about these two graphic cards, this is my computer information incase you want to know if my cpu is compatible or could handle the graphic card ( like i said before am new at this stuff )

System Operating system : Window 7 Home Premium
Processor : Intel(R) Core(TM)2 Quad CPU Q6700 @ 2.66GHz 2.67GHz
Installed Memory (RAM) : 4GB
System type : 64 bit-operating system
System Manufactor : HP-Pavilion
Computer Memory : Terabyte (1000GB)
Current Graphic Card : Nividia GeForce 8600 GT
(if you need more details about my cpu please comment back, and leave direction how to get to it :))

Also if you want more information on the graphic card go to the links below

Nividia
EVGA nVidia GeForce GTX 280 1 GB 01G-P3-1280-AR - eBay (item 260532674264 end time Feb-02-10 16:49:59 PST)

Radeon
XFX Radeon HD 4890 Video Card - 1024MB DDR5, PCI Express 2.0 x16, CrossFireX Ready, (Dual Link) Dual DVI, HDTV at TigerDirect.com

Thank you for your help!

something to consider here is your power supply I did not see a spec listed for what you have but you need to make sure you have a power supply that will run a high power card correctly a lot of people overlook the power supply but it's actually the most important piece of equipment in your computer.

you need to check power requirements of the card you intend to buy I can tell though what you want is a single +12 volt rail power supply design to run a high power graphics card don't buy into all the multi rail power supply hype get one that can deliver at least 25 Amps of current the more the better don't get hung up on watts only I would recommend PC Power and Cooling or Corsair power supplies both are really good power supplies.

Also my vote go for ATI brand video and DX11

+1 to computersplus, only I would instead suggest 34 amps on the +12 volt rail, or higher; it's also got to run the rest of the rig.

This is just a personal preference, but if it's between the two cards you listed, I would go nVidia... if for no other reason than you can be almost assured their driver team will put out some sick new driver in a month or two that will really increase performance; whereas with ATI, not sure what it is, but their drivers have always been... well... not inspiring.

That's actually a choice I'm weighing right now. I got my 88 3 years ago when they first came out and it's high time to retire her to another box; although, truth be told, there's no compelling reason yet other than, "I want a new one". It'll be easier when Fermi drops... cause I really really want one of those.

I moved from the NVidia 9800GTX+ up to the ATI HD5770 and I am very impressed, it wasn't expensive £115.00 ish and it is quiet and cool using less power than the 9800 and I can turn up lots of settings in all my games using anti aliasing in most with no lag , also dual display is great to my HD TV using the HDMI output with sound included