I know theMist King system is very popular on these forums, but for someone who only has one Cham and no others in the foreseeable future I really love my exo terra Monsoon. It comes with two nozzles and a nice compact reservoir that has a built in timer.
I was having problems with gnats as well in my store bought organic soil. The problem is that organic soil contains animal manure. I now use pure Eco earth for my potted plants, sometimes with a bit of play sand mixed in. So far this has worked beautifully.