Sorry for the sleeping dogs video misspelled the words
my bad. Well i actually was still stuck at ~30fps with FX6100 & HD7770 as i recently completed this game.
In windowed mode it's 60 fps settings maxed out in both the cases in sleeping dogs.
So you ought to have HD 7750 or comparatively above in either amd or nvidia for good medium settings gameplay for watchdogs. Also OCing might help with a good cooling system.
Well i recently tried AC4 (from Ubisoft; developers of WatchDogs) & works good not great at max settings. So you might have got an idea but feel free to ask further before choosing a solution that might help others.