I just bought a Geforce card from Kustompc and I must say it's great value. A Gainward Ultra 1600XP Golden Sample for just under £200 including VAT. This is a 5900 Ultra card with 256 MB memory and it comes with a nice bundle. Included in the box are a 5.1 sound card, a 3 port firewire card, optical and svhs cables, a little pair of headphones and a firewire cable. Nice
I know better cards are available and DDR3 is making an appearance, but I don't need the cutting edge.
I have this card with an athlon 2600, runs Far Cry no problem, but only at medium settings, if you put them up to max @ 1024x768 you can feel it slow down too much.
I've had this card for about 8 months now. If I was buying one now, I'd look at least at the new nvidia5700, it gets good reviews at the moment on 'bang for bucks', but it depends on how much you can get the 5600 for.