Do you like the 40-ish mm focal length? That is the big question. The FA 43 is a great lens, but it isn't really a normal lens on crop frame. The DA 35 would give you a similar focal length to the Sigma (although it is slower on aperture, has macro/close up ability and is sharper on the edges).
It is hard really to make a recommendation, since we don't know what you feel that weaknesses are of the Sigma that you wish to rectify. The FA 31 would probably be the real answer, but it's kind of our of your price range (I know it is out of mine).