What rx 570 8gb model gets 30MH/s

I’m new to gpu mining and im still trying to figure out which parts should I pick. I was planning to go for a rx 570 8gb x7 rig but I would like to see 30 MH/s or even more or minimum 29 MH/s. What rx 570 8gb model should I take?

Why not consider the Rx580? With modding you can get 31 MH.
You can get MSI.