I was under the impression that Snakeheads were illegal in the US..
I know Florida has become overcrowded with these and some aquarists take them right from the wild, but I'm not completely sure thats safe...
Snakeheads are wildly aggressive and strong. They also get to be pretty large, (unless you get a dwarf) they get to be about 3ft, I would be worried about anything in a tank with a snakehead.
Alas, I do not have personal experience though, this is just from years of reading forums.
I will bump Oddball's questions though, and add; How big is the tank you plan on housing them in?