I have yet to try the shorter tower and and shocks. So I can't say how small or big the change is going to be. Looking at the lengths of the shafts that Schelle is offering its about 3mm in shock body length (this is a complete guess, just doing the math based of the shafts we have been running vs what's going to come in the kit) Note also the lower towers will become more and more noticeable the higher the grip the track is, it may not be as noticeable to someone on a rough loamy track where as someone running on super high bite clay may say its the best thing since sliced bread.
If it were me looking to hit the high notes of the updated car, I would start with the 17mm out drives and the universals, new rear arms (may not hurt to pickup all the arms as it is going to be a new plastic) and then the new RWB chassis in that order.