Info: - Efficiency scale of Mining Amplifiers - PlanetCalypsoForum
2) you should test if lower "efficient" Terra amp 4 (eff 17.5) or higher "efficient" Terra amp 5 (eff 22.5) are even more optimal for that area. Especially taking into account if cheaper market on that new for you mining amps. Be flexible and always keep hand on pulse of market on amps you use and materials you supply.