if you would take the time to think out a budget, measure your room size, and tell us what % of home theater/music use you will be doing, you wold save yourself the 10000 questions you have asked.
Most of us around here have heard store bought, internet direct, and do it yourself subs. The best value usually goes to diy if you are good at woodworking and have the right tools and knowledge to build your own sub. ID subs almost always are a better value and better sounding then something you can buy in a store.
So hash out that budget and grab us some dimensions! Stat!