I need replace the B&G SLC25 that started to leak on me. I would like to replace it with either a Grundfos Alpha 15-55 or Wilo Stratos ECO 16F. Are these comparable pumps and are they the correct size to replace the previous pump. I think the variable speed pump should be helpful as there are three zones on the line to the house.I'm trying to be green. Thanks for your help. Jim