You want to get a DDR3 one - their more expensive, but trust me - DDR3 memory makes all the difference; I know
Unfourtunately, however, your looking at £100 for a decent 7600GT.
I've got a 6600GT - not as good as a 7600GT DDR3, but much better than a TurboCache 7300GS. Take a look around - I bought mine for £80 about six months ago, and if you could pick one up for £60 it would be a bargain.
Otherwise, save up and buy a 7600GT DDR3 - you'll really see the difference