What motherboard is it going in. Do you have 8x AGP or PCI express. Either way you should not need to spend more than £180 for a good card.
You should be able to get a Nvidia 6600GT for less than $200, maybe less than $150 depending on where you go. It's a good mid-range card. I recently got one for my teenager's PC and he can play all the latest games at full graphic settings, such as Doom 3 or Halflife 2. The more expensive cards might give you a better framerate, but that one is fine and gets a decent rate, very playable.
