By your comments, I'm almost tempted to stick with AMD and get anAM2 5000 @ £200.
If you are truly not worried about the cost, get that e6600 for only 50 pounds more... Right? Again, if cost is not a big deal and you wish to build a powerful gaming rig as you said, why build a weak gaming rig? Why no SLI? Why 7900 Gt? It is no longer the number one card. Finally, you must be aware that new generation video cards are only 3-4 months away (unless you are planning to get two new generation video cards for SLI or CrossFire when they come out and move the 7900 Gt to the third slot...) In any case, for now 50-100 pounds should not be the deciding factor in your CPU purchase. Get the best and it will improve your sysem's longevity. While that AM2 5000 may be adequate for some time and unlikely to become a bottleneck for a while, a stronger CPU will take longer to show signs of weakness.