So they are taking the card back and not giving a replacement? What is your budget? If you are in the US or Canada Newegg.com is the place to go. Id get a 5750/5770 card and just be done with it. They far out perform an 9800gt card. For $150 here is a good one with free shipping
Your PC is just a little slower thah mine, so a 5750 would be perfect for you. If your budget is a little lower, a 5670 is also a sweet little card, just a tiny bit slower than the regular 9800gt but much more efficient.