I think you're choice of processor is fine, AMD may not compete with intel in top performance, but they are always great for value, and atm that processor is on offer with a mobo for $45 off on newegg, so it seems a good choice.
You could have spent over $100 less by going for an AMD6000+ (3.1ghz dual core). Performs every bit as good, frankly. Especially if all you're doing is playing WoW and some other games. Your Videocard was fine for WoW, so doing the whole mobo/CPU/RAM upgrade was a good move; the videocards will come down in cost over the next months anyways. Since you already have an 8600, the next logical step for your money would be a gtx260 (they're coming down lower and lower in cost). So just hang onto your seat for a while.