Is more watts better for a subwoofer?

I need to buy a subwoofer for my new home-theater system, I have various options, but I don�t know how to choose between them. Is it better if the subwoofer has more watts? (dynamic and continuos power) Is it better if the lower -3db limit is the lowest and the upper -3db limit the highest?? Price is not a problem, so it can be as expensive as it gets. Could you as well help me out and give me some options? So far I�ve checked only POLK AUDIO