I think too. I have [email protected] and 5850 and it plays all games fine and don't think I need to upgrade my cpu either.
SB is only good mainly if doing lots of 3d rendering, video editing, photoshop work, cadwork etc. For gaming a good decent quad cpu will do and as mentioned people will notice more improvements with better graphics card.
If you were talking mainly about the 2600k, or you already had the first-gen i7 oc'd to 4GHz, then I would agree. The 2600k is a beast once oc'd past the sweetspot of 4.6GHz, its hard to match on price if your after a new setup for rendering/image manipulation as you mentioned WingZero30. The 2500k on the otherhand is perfect for mainly gaming and is a bit slower for media productivity because of the lack of 4 threads. If your patient or don't do much media then the 2500k still worth considering to save yourself £75.
Your GPU is perfect for your setup as you won't notice any bottlenecks in that combination. I bought a 5970 (overpowered for my CPU but a necessary purchase) because games were getting very sluggish on medium settings with a 4870. From all the games I ran, I've found the potential of the 5970 in combination with the QX6700 is only 65-70% because even though the GPU can handle higher graphic settings, the CPU is hitting 90% from the game alone. It doesn't help some of my fav games are badly coded console ports such as the resource hog of GTA IV.
