With the build you posted, you have a future proof CPU, and possibly motherboard.
With the build Muffin posted, you have a rock solid build for a while, but you'll be lacking in USB 3.0 support in the future, and SATAIII which will become the standard for newer hard drives in the future. You'll also be losing 2 more processing cores. Not sure how quickly newer games will be able to take full advantage of these (if any don't yet, anyway), though.
BUT! You'll be getting a much more powerful GPU, and faster RAM with better tighter timings.
Personally I know you're lacking in the CPU portion, and it seems like you don't upgrade all that much, just like most of us. I would go with the build Muffin listed, as it will be able to **** near max out most games now, and still be able to play newer titles as they come out. Mainly because of that more powerful GPU.
However, you could save a little money on the build Muffin suggested by going with a 4850, and throwing it and yours into Crossfire, and have a MUCH more powerful system. For quite a bit cheaper.
It would come out to £372.43 including VAT if you went with a 4850 instead of the 4890.
The 4850 that I used as comparison (from the pictures, it looks like a PowerColor) :
Arianet ATI Radeon HD 4850 1024MB GDDR3 PCI-Express Graphics Card - Aria Technology