TWC Houston uses a two stage set up. The first box is your "regular" digital cable STB (in my case Motorola/GI). The output from your cable box is then fed into a HD decoder (again GI in my case). The HD box decodes HD and DD5.1 as necessary, with alternative component-video or RGB output to your TV. If the signal from the cable box is not HD, the decoder passes the signal through. The box also has seperate audio outputs for "regular" audio, as well as decoded digital audio. I think that the box functions well, although the signal occasionally drops (particularly on HBO). the loss of signal could be due to the transmission, rather than the decoder of course. The charge is $3.73 for each box (i.e. 2 boxes are neeeded for HDTV, only 1 for digital cable).