RE: hooking car subs up in house
It depends on the sub you are planning to use.
If it's just a speaker in a box then you need nothing, just hook the speaker up like any other speaker.
If you are using a powered sub then you will need a 12 volt power source. And not just any 110V to 12V converter. You will need one with a very steady/filtered 12V output that will maintain 12V at the power levels the sub will draw. Those kinds of power supplies are generally pretty expensive.
In short, if you are just using an unpowered sub, you're good to go but if it's a powered sub you'll probably be better off to just get a regular surround type sub.