Depends.RipleyK said:
Really going to depend on the layout of the house and where the receivers are.
In some cases, it will be impossible to run a second line to some locations short of cutting out sections of drywall/plaster/whatever to open up a wall.
That being said, you could replace your current switch (assuming WB68) with a SWM8. That will give you dual tuner use on both your HR2x. The Tivo unit is SOL for the second tuner unless you can get another line to it. The Tivo and the old Phillips units would have to be run off the legacy outputs of the SWM.