I have one of these:
http://www.razerzone.com/gaming-audio/razer-blackshark
Decent sound, it's pretty durable and doesn't require any additional drivers (just plugs into your headphone jacks).
I also have one of these:
http://www.plantronics.com/us/product/gamecom-780
This one is pretty good too, but it's made of more plastic than metal, also fits a little tight on my head (but I have a big head). It also uses USB, so it would be dependent on drivers existing for the mac, which I'm not sure there are.
Overall, I think the plantronics actually has better audio, but the razer is more comfortable. The important thing is to consider how much time you're going to be using it. If it's only a couple hours a week, I'd just get a $20 wal-mart one. It's WoW, so any gains you'd get from the emulated 5.1 wouldn't be worth the probable compatibility issues you'd have with anything USB based like the plantronics. Otherwise, I would recommend the razer, especially for general compatibility purposes.