I recently (Nov '06) got a Sapphire ATI Radion X1900 XT 512Mb for just over 200 GBP and as of late last year it was supposed to have the best performance/price ratio on the market. Has no problems running half-life 2 with high graphics settings but I guess there is something more recent out by now. I use it with a dual core 1.9 GHz. Hope that helps.