A:
Yes may ABSOLUTELY replace your cable boxes for Tivo. Unsure how familiar you are with Tivo, but there is a small investment upfront for years if cable company savings. The TiVo must be purchased as well as a lifetime subscription per box . Check that out on TiVo.com .
The first configuration I had was the most simple. I had the main TiVo you are referring to in my living room and connected Tivo Minis ( x 2 ) in two other rooms. Via my home network I used 2 of the TiVo Plus' tuners to watch the Tivvo Minis. It's great!! The best part about this configuration is that the TiVo Mini comes with lifetime service so no need to pay anything aside from the purchase price of the Minis. BUT they MUST be used in tandem with a "hub" ( any Tivo Roamio box ).
Last but certainly not least, you do need a cable card from Comcast to make it pick up your channels. It also supports OnDemand! Which is awesome! The first cable cars is free and any additional is around 1.50 month. Make sure to pick up an M-Card so it has multi stream capabilities. ( hence the M ). DO NOT LET ANYONE TELL YOU TIVO IS INCOMPATIBLE WITH COMCAST.
Please respond if you'd like more detailed instruction or advice on the subject. Long live TiVo!