Thanks for the ideas. It turns out that Mediacom lied about several of their services, they said their STB DVR could be networked, but when the guy came over and we asked about what we were told we were getting, he claimed they were incorrect and it wasn't possible. So we told him to take a hike because we weren't paying them for services they said we were getting but actually wouldn't (only Fl and a few other states get what was advertised to us - HDTV, On-Demand, free Premium Channels, AV networking etc).
I think we are just going to get Netflix and if so, I only need to run one CAT6 cable through the wall to the TV or Blue Ray player and into our router. Doesn't solve me not being able to watch TV on my laptop through the DVR without having to run several cables through the wall via S-Video and Composite Audio but I suppose I will figure something else out.
On the other hand, if we went for TiVo (still trying to convince my mom it's better and for the same price Verizon is charging for renting their POS) I could patch that DVR-STB to my Router and stream it to the computers that way and still get TV without another expensive DVR-STB and use our networked EHDD as the media server and get another one for other backup etc. files.