I am not sure anything will speed up a slow connection, except getting a better connection. Twx has a couple of variations, one that runs on java and one that is downloadable. I used both, and they seem about the same. Switching to cable is helpful, as is getting more RAM for your PC.
I haven't tried Sierra with IB, but I have been using Ensign. Personally, I don't think the IB feed is that good. The Ensign people stated that it is not the best, and the Sierra people don't recommend it. So I don't have anything better, except to pay more and get a live feed from DTN or ESignal, then Pay exchange fees