Hate to break it to you AMD guys, but an E6300 whips an athlon II 240 like a red headed stepchild. I've owned an E6300, and an Athlon II 245, and of course my Phenom II 550. The E6300, clocked to 3.8ghz performs about the same as my 550! Athlon II 245 at 3.8ghz is not even close to either really.
Clock for clock, the core 2 duo's are faster. Pentium dual core's are about the same as Phenom II 545 and 550's if they are clocked the same. And the new wolfdale celerons are decent, probably still even better than the Athlon II's although I'm sure thats a much closer race.
I was not impressed by the athlon II, at all. Thats why it's gone already.