Thanks Ernie for the insight - a couple of follow-up questions, if you don't mind:

So, I am thinking of two HD DVRs - one "local" to my HDTV, and one "modulated" to be distributed through the home video network. The only High-Def viewing I would have is off the local family room receiver, which would have a single coax going to it, and then to the TV through component-video.

The modulated DVR, in the basement, would only be "feeding" non-HD TV's. So, are you saying that the simple fact that the receiver puts out channels at a number higher than 100, this would conflict with the modulator, assuming it does not go that high (that's something I haven't checked yet)? For example, if the "normal" channels go from 2-80, and then the HD channels start at 100, I could not use 90 for the modulated channel?

Another question - I figured I'd have two coax lines feeding into the video network (through a splitter): the regular cable line, and the line from the modulator (with the digital cable DVR connected). Hypothetically, let's say that is modulated at channel 89. My assumption is that on a TV connected to that network, I go through it's internal cable tuner, and every channel up through 89 is showing the "standard" cable channels. Once I hit 89, it is the modulated digital cable signal, and is now controlled through that "central" receiver. Is that right?

Again, thanks for the responses - there's just no way to get these kinds of questions answered through the cable company.

With all these issues I am thinking of, along with your feedback on the cable boxes, I'm already thinking of just sticking with DirecTV and waiting for local HD availability (which is my #1 priority in all this).