Rather than a bunch of links from HardOCP ( you can dig those up yourself ) here's a
gaming-CPU analysis for July which considers price-point and performance -- be sure to insert your own prejudices, of course.
It's hard to consider WoW in terms of 'cpu intensive gaming' (it's 32bit, runs on one core, etc) it still is worth looking at more robust hardware just terms of longevity. For WoW, though, you're probably more likely to get choked on RAM (aka why-I-hate-Dalaran), rendering, or throughput even on a somewhat dated processor.
Dual-core will do ya plenty in terms of WoW, though quad-core gives you nice options if you -- man, I hope it's legal to say this -- play something beyond WoW (some of them will happily use 2 or 3 cores).
Whatever you get, for the love of God, make sure it's balanced: you'll generally have a better system you're happier with using mediocre but balanced parts than some great stuff and some 'well, I put all my money into the other parts' parts.