Best Truggy setup

[Rebelgium]

I'm planning to do a conversion on a Hyper ST or a Mugen MBX5T.

I know that higher voltage combined with low Kv setups are optimal.
I'm going to stay with 6s and not go higher, because if I'd go higher I'd need a more expensive ESC. The MMM and HW Xerun can handle 6S, but no more...

So to operate at the optimal rpm I'd need to get 1600 -1800 Kv right?

So why does everyone keep recommending the MMM 2200 combo?