Mamba Max and 5S?

hiya all, sorry to ask this, sorta new to this and just try`n to read up as much info as i can before i go out and buy a truggy to convert. At the moment i have a crt .5 conversion, so its easy to run my MM on the 3s to keep that truck run`n along, but i was looking at get a thunder tiger st-1 and putting in a neu 1515/2.5 and get a 5s, but was wondering if i should get a new ESC as well or can i stick with the MM. was reading the post on this threads but some of the stuff sorta flew over my head. thanks for any of the help, like i say not in a big rush, just try`n to find out what i should save up for. hopefully by the time i decided to get all this, the MMM will be out.