you have both AGP an PCIe cards listed. your PC will support AGP or PCIe cards, but not both. So, first you need to figure what can go in your PC.
As for the cards, you've got cards ranging from $50 to $200. You should pick a budget and get the best card for that budget.
Oblivion really dogs GPUs and is ATI friendly. If you must have HDR enabled, budget at least $150. Here's how various cards fared with the game: http://www.anandtech.com/video/showdoc.aspx?i=2746&p=6
$200: Radeon x1800GTO, 256MB
$175: GeForce 7600GT, 256MB
$150: Radeon x1600XT, 256MB
$125: GeForce 7600GS, 256MB **
$200: GeForce 6800gs, 256MB
$140: Radeon x1600pro, 512MB **
$150: GeForce 6800xt, 512MB **
** = HDR supported but makes games unplayable
I am getting a new video card.
Mostly for gaming.
But I dont now wich one to chose and i dont want it to be too expensive.
Here's 4 alternatives, feel free to suggest something else.
PowerColor Radeon X1600PRO 512MB DDRII, AGP8X, DVI-I/Tv-Out, Retail
Sapphire Radeon X1800GTO 256MB GDDR3, PCI-Express, ViVo, 2xDVI-I, Lite-Retail
Sapphire Radeon X1600PRO 512MB DDRII, AGP8X, Tv-Out, DVI-I, Lite-Retail
XFX GeForce 6200A 512MB DDRII, AGP8X, Tv-Out, DVI-I, Retail
Must be able to play games like Elder Scrolls IV: Oblivion.
Must support HDR.