Good point Hugo. I too would like to find this out. I am currently running an Nvidia 6600 with 256 ram and looking at data I found on tomshardware.com, relating to frames per second, My 6600 is slightly slower than your x1600, but not much. Both cards are definitely closer to the bottom than the top, but how high do you need to go. Sure bigger is better but the higher you get the more disproportional the price/performance ratio gets. I also would not like to spend to little and be disappointed. I have also had suggestions that a card with greater ram may be better, though from what I have read this my not be as important as other speed related features of the card.
Any outside knowledge would be great
Denny