[damien c]

i would go for a ati 4870 unless you wanted to go sli later on if your board supports it no point really going for, a gtx xxx series card unless you want a 285/295 and even then the 285's iirc are only outperforming the ati cards in certain games and apps, also dependent on price and what you would be willing to spend look at the 4890's.

4890 £195.98

4870 £160.99

gts 250 £166.74

gtx 260 £156.99

gtx 275 £235.74

gtx 285 £310.49

gtx 295 £442.74

list there of the cheapest and also the one's that are in stock of the cards as well, as you can see by the prices of them the 48xx cards are very cheap compared to the nvidia cards the 4870/90's are ati's top of the line single gpu cards, and they are far cheaper than the nvidia options and perform around the same.
seriously though go for the ati card as i have 2x bfg gtx280's in sli and to be honest yes it's good at high res and high detail gaming, but when you think that i get probably only an extra 10-20fps over the 2x 4870's in crossfire on in crysis and only an extra 5-10fps on just the 1 card and that is the most graphically, demanding game that i know of then does it really seem worth it to you.

as most people on here know i like nvidia and always will but if your looking at spending a fortune, on graphics then go for nvidia but if you are sensible enough to not spend a fortune on a graphics card or cards, then ati is your best bet they give top of the range nvidia cards a serious run for there money and only just loose out and, considering they are almost half the price it makes more sense to buy ati at the moment than nvidia.

also just to add you shouldn't buy them from overclockers but i have them on a bookmark so faster to get to.