Just to clarify- the 600 bb would not be the *best* you can do for an upgrade , but it will make a nice combo for it. It all depends on your goals and what battery you want to run. If you want *ok* run times and run 6 cells, then go for the first one. If you want 7 cells and short run times but a fast boat, go for the third (the race one). For most people just playing around, the middle one should do it for you .
Joe