Well, since I have access to cheap electricity, efficiency is the last thing I care about.

Importat factors for me are  being cheap and having higher TH as well as reliability and durability inorder to have better ROR , that is why I am not thinking about M20 , M10 or cutting edge miners, with same amount of  money I can buy few low efficiency miners which will sum up in more TH just I need more space to put them  which I am ok with it now.