I did something similar with my 6800xt since after playing along with overclocking the card, I decided I don't need it in anything I play, so went also to 2200mhz (lower wont work for some reason), and now it barely goes over 100w if I keep it locked at 60hz, and around 150w if I stick to the 100hz of my monitor. Its amazing how these cards can be so super energy efficient if you downclock them a little bit.
My whole PC now uses somewhere around 240w, that's basically console power usage, for a much more powerful system. It would use even less if not for the water pump and the 6 fans