In my mind, there are three types of music that are great compliments to WoW. First, there is the grinding/farming music that for me, is usually relatively mellow. Second, there is PvE dungeon/raid music that is a little more upbeat, but like the encounters they sing to, aren't too fast melodically and can even be a bit drawn out. And finally, you have the lightning quick, booming music that is totally win with a side of PvP.
Not all types of music fall distinctly into one of these categories, and can often even fill two of them nicely. One such example is this week's SotW, which works beautifully for both PvE and PvP, imho. It's a little song by the name of Denied, by the great Swedish band Sonic Syndicate. The video is very low-budget and not-so-good, but the audio is where it's at. Enjoy. =)