Four cores at 2.93GHz and enough headroom to take it to 3.4GHz before it gets whiny.
That's 555 fps in S.T.A.L.K.E.R at 800 x 600 (and 620 at 3.4GHz) - the next best is the Q6600 at 454. With the exception of its new brother the QX6850, nothing else gets within spitting distance.
But over £700? Nuh-uh, especially as S.T.A.L.K.E.R snatches under 10 fps extra at 1680 x 1050 over the Q6600 on a GeForce 8800 GTS 640MB. So, you need to match this by spending on SLI too.
The just-out QX6850's pre-order price hints at a price drop for both chips, so wait a month or two. Even then, if you're blessed with a P35 or 680 board, buying the QX6850 instead is a no-brainer.