I think it would be helpful if you could explain a bit more in detail what you are trying to accomplish.
ARe you planning on streaming content from your computer to various TVs? Why would you want to use an HDMI cable to several rooms from one computer? You would have difficult time using a computer somewhat remotely.
A hard wire network is the best way to go. You simply have to make what are called home runs to each location from one common point, often called a wiring closet. This is where your modem and router and possibly a switch will be located. Any internet information is fed around the house from this point.
At each end of the wired run in various rooms you can add another switch and add as many components to that location as you like. In my main viewing area I added an 8 port switch to handle -TV, DVR, DVR2, Blu Ray player, Seagate streamer, Onkyo audio receiver, and an occasional hard wired connection to my laptop. I have a somewhat scaled down version in my bedroom, library, and basement.
If you are running wires I'd opt for CAT6 and Gigabit switches at this point. You can either buy the cables quite cheap at Monoprice or make them yourself. I do a bout 50/50 - I have made a few bad cables,there is a learning curve.
Are you factoring in any OTA TV reception? If you use Windows Media center with TV tuner cards you can record up to 8 things at once. However it is in a proprietary MS format, that only the PS3 will display. There are simple software conversions available but it is an extra step. If you record OTA you may want to look at other software besides WMC.
While Roku boxes are great at supplying internet content, it seems they fall down a little as a network streamer. there the basic stuff like WD , Seagate, and more expensive Dune and others shine. These are for streaming content you have ripped or recorded on your computer or NAS. If you go this route you will need lots of hard drive space. I'm running 3T at the moment and I"m not using raid which I should be. Rumor is hard drive prices will be going up soon, so bear that in mind.
So, think about what you want to accomplish. Truth is you will NOT have an experience similar to using DirecTV. AT this point it is not smooth and seamless, and you will need a good high speed internet connection, I"m on a 12M connection and it works well, you might be able to get by with less.