I went from a max pro / tekin 400kv which was good , to a viper copperhead /4500 which was better , to a hobbywing xerun 4700 sctpro combo which has made me very happy. I have all the power I could possibly use at my track. I think in SC trucks , the controller is more important sometimes then the motor itself. There are some huge current demands in this class.
In response to the gentlemen looking for a system for his son to try next , consider that viper 4500 system . It was a very very nice system for the money. The esc is one of the best made i have seen, and its much smoother then unsensored castle systems I have owned.
I have the MIP turnbuckles that come with the proformance chassis. If they are the ones you are asking about, they are nice, not as sloppy as the stock ones . But i dont think I would buy them unless I already had to replace the stock ones .