^ forgot to mention, get one with an aftermarket cooler as the 4870 can be a little noisy. If you get one with the stock cooler than raise the fan speeds a little to keep it from getting to warm, since once it does that's when the fan speed really kicks up.
Meg is right - and the 4870 will be two to three times faster than the 9800GT. If want an nVidia comparison, the 4870 roughly falls between the nVidia 250 and 260. Have you looked at the THG charts?
Hi it's the thread starter here, i somehow forgot to activate my acount so it disapeared :S how ever. If i want the best cooling system on the 4870 wich aftermarket producer should i take? For example MSI, XFX or Asus?