Replacing cable boxes with DIY home theatre setup



I am fed up with paying comcast each month for cable boxes and was wondering if I could instead make my own system with a server that would act as a backend/frontend and two other frontends. I would only like to use one cable card and have DVR functionality so I would like a 4 tuner card. I was wondering what would make good inexpensive frontends and wouldn't be too massive. I have an old Dell optiplex gx270 with a 2.4ghz Pentium 4 and only 512mb of RAM (I will possibly add more if need be. The server would be hooked up to an SD tv with component, Svideo, and standard RCA connections. One of the frontends would be hooked up to an HD tv, but I have no intention of streaming HD content from the server. The other frontend would be hooked up to another SD tv the same model as the TV with the backend. Both frontends would have to be wireless but the server would be hooked up to LAN. I am experienced with linux and would be perfectly fine with installing linux on the systems instead of windows. They don't have to be actual PCs. I was planning on using XBMC for the frontends but I am stumped as to what should be used for the backend software. What additional equipment would be needed, I.R remote, etc. To make this as seamless as possible. Any help is appreciated.
Media over wireless just seems like asking for trouble. I think you really want to go with a wired network set up. Now I understand it may not be possible to run Ethernet cable to each front-end location, but since we're talking about replacing cable boxes, I'll assume that there are coaxial outputs at each location.

If this is the case, then I'd recommend:

1) Ceton InfiniTV6 PCI-E or Ceton InfiniTV4 PCI-E
2) ActionTec MoCA Ethernet to Coaxial Adapters
3) 2x Ceton Echo

This set up allows you to watch live TV and/or recorded at any location. The front/back-end software is very similar with Windows Media Center. Remote controls are included with each Echo.

-Wolf sends

-Wolf sends