Agent > Warrior=Knight >> Bounty Hunter >>>>> Inquisitor
My 2 cents; haven't played the other 3 far enough to judge. Warrior and agent are both great choices as far as the story goes, but warrior gameplay, even if you don't pick your mirror AC, will be very similiar to your knight, so agent is my recommendation.
I see you have a fair number of level 50s, including a Warrior. In comparision to the Knight, how is the story? The Knight is the ultimate defender and hero of the Republic. Is the Warrior the opposite of that? A war monger that is waiting for the perfect chance to dismantle the Republic and herald a new age of Sith domination?