Best controller upgrade

Im looking to upgrade the controller on my surron, right now I have a stock battery & controller on my bike, I just want to upgrade the controller for now just to push some more power out of the battery and have more fun. Eventually, I am going to upgrade to a 72v.. But that's in due time.

Is there any good controller on the cheaper side that wont fry the surron stock battery but also have enough power for the full potential of the 72v battery?