I put a 4800se in a AMD64 at weekend and it ran doom3 really well. (similar to a 4600).
But do bear in mind that they are driectx8 cards and may not run some other games as well as newer directx9 cards.
Given your budget though I'd go for a 4600, untill you spend around the £130 mark the other cards arent much better.
Intel Core2Duo 6400 @ 3.4Ghz
4GB Geil 6400 Ultra
3 x 500 Gb Samsung HD
EVGA 8800 Ultra OC