Which games do you anticipate playing? Your only upgrade options on that motherboard is a Quad at 3GHz which you will find tough to locate.
A Q9650 is 3GHz but is still listed at about £200-£300 most placeshttp://www.amazon.co.uk/Intel-BX80569Q9650-Q9650-Core-Processor/dp/B001D86S3G
For that price you can get a MB, CPU and new RAM that will perform better I believe. I'm building an AMD A8 computer for under £250