Your mobo is capable of supporting PCI-e x16 graphics card, so I would suggest paying a little bit more and going for the 7600, which ranges from about £60-£100 depending on what you go for i.e GS, GT. I linked to Overclockers here in the UK, they can be a little bit more expensive but they offer an excellent service and returns policy if you need it. Out of all of them I would pick -
BFG GeForce 7600 GT OC 256MB GDDR3 TV-Out/Dual DVI (PCI-Express) - Retail (GX-019-BG) £99.99
But if you didn't want to spend that much then the GS versions will be fine and at £61.99 you can't go wrong really.
The 7300 you listed doesn't really cut the mustard especially with new games such as PES6. The 7600 will last you a good while and is capable of running most new games on med settings and resolutions. If you wanted to spend alot more then go for a 7800 series or 7900 series and if you want to spend REALLy silly money then there is the 7950 GX2 series. Just make sure that you have a adequate power supply, I think a 430w-450w PSU should be fine for a 7600 series card. If you have to buy a new PSU go for a branded make such as Antec or thermaltake. If you have any more questions or your not sure if your PSU is powerful enough please post back.