I have four old different brand receivers in the same room with MLB EI. This year, because of the lack of memory capacity in these boxes, Iam unable to view any of the games in the 700's where they always were. Now I must upgrade all of the receivers to the same DirecTV brand meaning they will all be affected at the same time. What exactly do I need to do to continue to separetly control each box without affecting another. I don't have Hi-Def but not sure if that really matters because Hi-Def boxes convert to standard and not really interested in a DVR model, so what model receivers will I need?