RE: might but a 18t
You can get a ft 18t and put a mamba 6800 and a gp bat. It will run fine. The diffs will be fine also. You don't need MIP superdiffs or even MIP cvd's, but they are nice to have and allow you to upgrade the power more without upgrading the tranny.
I run a 7210kv motor and a gp bat, I run stock diffs and cvds. I don't even need the cvds, I just wanted them. My diffs work great and never strip.