The motherboard has a x16 PCI-E slot, so no problem there. It'll fit physically too if it's not a slim type case (as shown in the pic click here), but unsure if the PSU will be up to the job.
Does the PSU have at least 1x dedicated 6pin PCI-E connector? If not, you'll need to be looking at upgrading the PSU as well, for £30-40 extra.
If you don't mind me asking, how much are you going to be getting the 9600GT for? For £62, you can get a slightly better HD 4830 click here. G