5.1 = five speakers plus one subwoofer = 6 total.
7.1 = seven speaker plus one sub = 8 total
When people speak of 8.1 or 9.1 or 7.2 they are using combinations of extra speakers and subs in the room. My Yamaha RX-Z1, for examples, allows for a full 8.2 setup with 2 subs and 8 speakers in the room. I use 5.1.
Built-ins (consoles)...
The biggest issues that I continually see with built-ins is the following:
1. They often hold all your A/V gear. If so, then the gear REQUIRES proper space and ventilation. Your 60" rear projecton television needs good airflow to the lamp, the HD cable/sat box runs HOT and needs solid airflow. Fans can be put in, or GOOD venting. Venting shows the gear, which doesn't always look good, and fans can be noisy, which is obnoxious. But, you gotta pick a way to do it. Small vents at the bottom and a small hole in the top? NO! It doesn't work that way, and you will cook your A/V gear if you think that's all it takes.
2. Your TV will break. Period. So, do NOT build any unit to 'perfectly' fit your display. Leave several inches, minimum, around the display so that when (not if) your display needs to be replaced, you have some room to work with inside the cabinetry. If you want that 'perfect' fit, then build the case slightly oversized, and then put a spring loaded false front on the built-in that perfectly frames the TV. This provides and even better look than that perfectly fitting box, and still allows you to switch the TV out at any time and have a new 'perfect fit' frame built anytime!
3. Don't crowd your gear! Beyond ventilation, you need to make sure that each piece of gear is on a dedicated shelf with enough room around it to fit your arm in and to get to cables.
4. Cut holes to route cables! Don't forget that one. The cables have to go up and down behind all your gear, so if the shelving is flush against the back of the cabinet you simply will not have any luck in running the cables up and down - then you will have to pull all the shelves out to cut holes in them on your own.
5. Don't put your TV high! Sit down, relax, pick a height - about 30" off the ground is usually a good height. The new 'look' is to have a plasma over the fireplace - but have no doubt, this causes you to crane your neck back and gives you a headache after watching a good football game or movie. So, be sure to put it in the most relaxing position possible!
6. Plan for the future with solid access from the built-in to your TV and make sure you run an Internet connection and all other necessary cables to the built-in location prior to construction. It'll save you numerous headaches down the line.
