Depending on the model of HD receiver/DVR you get, it may or may not have a composite video output (to feed a modulator with). If it does not, then you will also need a component video to composite video, or hdmi to composite video adapter (plus the modulator).
There is also an issue with the HD GUI (menu, list, guide, etc.) not rendering in SD from an HD receiver. So the remote TV will just get a big obnoxious message box on the screen anytime the menu, list or guide is called up on the HD receiver. If you never try to control the receiver from the other room (only watch but don't use a remote), then it will probably still work for you. You can search these forums for more information on this issue, there are several lengthy threads about it.