What makes a good whetstone set? What sets should I avoid?

I'm looking for a better knife sharpener for my hard steel chef knife. I think whetstones are the way to go, but most of the sets I see are 4 double sided stones. Do I need that many stones?

Is there a totally different type of sharpener that you have had success with?

Edit: I should add that I like my knife very sharp, and I have a few tiny chips in the cutting edge from a cheap drag-through sharpener.