I was thinking either fluxbox or xfce. With Arch I tend to prefer something a little more minimalistic so that it's possible to understand the framework. With something like gnome... that's just huge and I don't really understand what goes on with gnome...
It's a nice DE but if something were to break it would be tough to debug without outside help.
It seems super customizable, having however a more complex setup though.
On the other-hand what I read about fluxbox seems great too, Its configuration would seem something I could grasp quickly and there are hundreds of Fluxbox "styles which would add some eye candy which... lets face it.. make for a better experience than the windows 95 type graphics some of these WMs have.