Okay maybe not 20000 rpm over but I agree. I didn't give max Rpms much consideration. the MMM is awsome just came with a little bad r/c mojo for me.
My suggetion is for you to get a 10XL and gear it according to speed you want to be on the safe side or get a better quality motors like the NEUs if you have more money to burn like Neu 1515 2.5 d as my personal choice on 6s lipo
Brushless Jammin Truggy on NEU 1515 2.5 D on Monster mamba max with maxamps 5000mah 6s Lipo
Gorillamaxx Revo CF version on Mamba maxx ESC with NEU 1515 1Y on Maxamps 4s 8000mah Lipo