I am thinking of upgrading the AGP card in my main PC in about a month's time to maximise gaming performance. I currently have a Radeon 9800 pro 128mb (sapphire with HSI aftermarket cooler). I want to spend about £150 and was thinking of something in the Nvidia 6800 range. Would I get significant improvement by this upgrade (is it worth it?) if so which specific card would give me the best gaming performance (128mb, 256mb, GT, LE plain, Ultra)?