I have a thirty year old 30.7 cu ft side by side Sub Zero refrigerator/freezer in my garage that works well but is very poor on energy efficiency. I am not sure of the cu ft space of the freezer and refrigerator sections. The freezer section is usually 2/3rds full and the refrigerator part 1/2 full. I purchased a 7 cu ft. chest freezer at a big discount and as wondering size wise, what additional size refrigerator or top/down refrigerator/freezer would I need to purchase in order to have the same space for food items as I have now with the amounts full as stated above? Would you take a chance on a used unit made after July 1, 2001, which is the most recent energy efficient standard? I don't have a truck or SUV.