The OP should elligible for free postage soon:
http://forums.overclockers.co.uk/showthread.php?t=17943556
TR tested the latest Pentium G2120 and it had latency issues with some of the new games like BF3 and Crysis2.
Pentium dual cores cannot be overclocked and I would only really use one for a game like Skyrim or perhaps some of the Blizzard games.
I had a Core i3 2100 and when it comes to games which are multi-threaded it was starting to show limitations and the Core i3 3220 is not much faster. For instance in BF3 multiplayer the FX6300 is faster by 15% IIRC. All the new generation multi-platform engine can use more threads effectively and these include Frostbite 2,id Tech 5 and Cry ENGINE 3. Even Unreal Engine 4 will be able to use more threads better than the Unreal Engine 3 which is reasonably well threaded.
If I was not updating the CPU for a while,I would get an FX6300.
The Merc Alpha has good cooling for a budget case and can take long graphics cards fine.
With free postage the build will come to around £400. Now is the HD7850 2GB worth the extra £24?? Reviews show that the 1GB is fine with most games at decent settings,but I expect the extra VRAM of the 2GB model will become more useful especially at higher settings and with AA.
Edit!!
Here are some comparisons of the FX6300,Core i3 3220,Core i3 3240 and G2120:
http://www.anandtech.com/show/6396/the-vishera-review-amd-fx8350-fx8320-fx6300-and-fx4300-tested/5
http://www.xbitlabs.com/articles/cpu/display/fx-8350-8320-6300-4300_6.html#sect0
http://uk.hardware.info/reviews/331...iew-finally-good-enough-benchmarks-cpu-dirt-3
BF3 MP comparison against a Core i3 3240:
http://www.pcgameshardware.de/Battl...ld-3-Multiplayer-Tipps-CPU-Benchmark-1039293/