Oh my DK is Horde. And I enjoy my DK as a Belf. I want to try a mage. But I like Hunters a lot. Just I don't like Alliance really, if I made a Alliance.. it'd be druid or a hunter Night Elf... I want to go to a good server.. Silver Hand is just toooo boring. Also been depending on have dual-windowed WoW.. I am wanting to play up until the movie. Then quit again. Their are some classes I really want to play..
As for the server, it really depends. If you're PvE, less populated servers are great for exploring and loading time. But raids queue time will take forever. If you're PvP, that's where all the fun is! Kel'thuzad or Tichondrius.
Other servers to consider, Dalaran-US! That's a peaceful, but not so quiet server. At least the last time I was there, it was like that. Darkspear is good too.
I don't know if you follow WoW streamers but they're the big things in PvP. I once saw Sodapoppin (the Mage streamer) in one of our inter-server trolling.