Right i will start by asking what the reason your looking to change to a Intel chip?
Looking at what you have atm, you have your ram.. you got a mobo.. and a GFX card that your looking to upgrade.
If you are looking to go to intel i would go with RedDragons advice, without having the jump to the E7200.. intel wise the E5200 is the best bang for buck dual core atm.
Just to give you an alt option to think about.. staying with AMD and getting this.
http://www.ebuyer.com/product/149211
Performs on par the the E5200.. the both win and loose in gaming tests so they are pretty even par from reviews ive read.. and then going straight for the GFX upgrade just now with a HD4850.. ( not sure what you were looking for when you are going to update)... for your £200 it seems the best option / perfomance as WOW would run smooth without a flinch on a HD4850 / X2 6000+ and you already have 4GB ram so there is just another option to think about, but if your definatly wanting to move to Intel get the E5200.
http://www.ebuyer.com/product/150577 < GFX card btw.
Just a snipet to show you performance wise
http://www.xbitlabs.com/articles/cpu/display/core2duo-e7300-pdc-e5200_6.html#sect0
E5200 does better in Crysis, but as you said.. you aint playing anything that high end. And btw.. no flaming for this.. im just trying to give you options as you never stated why you were after a intel setup.