Ton,
Me, I would opt for getting high quality wiring done behind the walls for the system if possible. This limits equipment positioning, but looks a lot better. Trying to do this at a later date is more expensive, unless you are dealing with a basement refinishing job and drop ceilings. Your selected room dimensions are an excellent starting point. Consider a good quality cloth vertical blind to cover the glass door. This will reduce sunlight glare and upper frequency sound reflection. You might also require some room treatments.
Here are some other helpful hints I offer to friends considering putting in an HT system:
Home theater is really starting to come into its own. There are a lot of options with video displays, video and audio sources and speakers - I encourage folks to hit the HT stores to look at and listen to various set ups as a start.
If you are starting from scratch, visit good HT stores in your area, not so much to select equipment, but to see how the rooms are set up. There is a myriad of different types of set ups depending upon the goals for your HT system. Some rooms sound great, but look awful and vice-versa.
I encourage you to give thought to your equipment selection/positioning and furniture selection/positioning before room construction. The reason for this is you can run interconnects and speaker cable through the walls or ceiling. While this limits flexibility of moving equipment around, it makes the room look a lot nicer and has much greater WAF.
One of the more critical factors in you equipment selection is the video source - there are a lot of options - flat panels, monitors, rear projection, etc. It's tough to beat a quality 16:9 projector system with a good screen for home theater. Projectors are often ceiling mounted.
You should also think about where you want your audio and video source equipment positioned. Some people don't like source equipment under or next to a video screen or monitor. An A/V cabinet or built in cabinets on the side of the room offer a good option.
After selecting your audio and video equipment sources, figure out where you want your furniture located. With a projector system, primary viewing positions should be ~10' from the screen. Positioning furniture on the side of rooms do not offer optimal viewing and listening. Also furniture position can have an impact on sound quality. Once furniture is positioned, you can determine your speaker placement.
I have listened to a lot of HT set ups. It's tough to beat the sound quality of free standing speakers - but if space or looks are the primary concern there is always in or on wall speakers. Even Thiel and Joseph Audio, two highly respected speaker companies now have offerings.
The front center speaker is best located directly below or above the monitor or screen for realistic dialogue. Front right and left speakers adjacent to the monitor or screen. Five channel dolby digital processing requires the center speaker to carry most of the information - don't skimp on your center channel speaker. It is also important front speakers tonally match, as a result I encourage front speakers from the same manufacturer. Rears (in a 5.1) and side effects (6.1 or greater) are not as critical. If you need to save a little $ on your set up, add the rear and side effect speakers later.
Maybe a little more information than you wanted but hope this helps.
NB
