Got to ask, do you really want a DIRECTV Tivo HD receiver? Those boxes are based on a very old hardware platform and DIRECTV/Tivo isn't adding any new functionality to them.
I realize that this is a requirement here to question why anyone would want a Tivo, so I'll do the dance..
I have a genie ( with2 pups), 1 Tivo HD already, SWM connected. The Tivi will be on a seperate dish (for reasons having nothing to do with connections, networking, etc.)
My wife hates the Genie.
No that's an understatement, no Tivo no Directv.
As for me, the genie interface is not always intuitive, its runs a bit slow (it is a 34), but its "ok".
After joining Directv in 1993, I've had the fun of playing with several receivers, dishes, etc., my dream setup would be a networkable Tivo.
But if wishes were horses...