Learning my way around the car--so what are these?

[mgerity]

So, my RS 6 didn't come with an owners manual (BTW, anybody know where I can get one, in either paper or pdf format?). I've come across a few things that I can't quite figure out. So, what are these:

There is a hole in my center console in the tray behind the mirror adjuster. What is supposed to go here?


Directly behind that tray is another one, which is under the armrest (not the one inside the armrest, but the one under it). The front of that tray is blocked off, with a small plug located on the vertical wall of the block. I've provided a picture of the entire tray, and then a close-up of the plug. What is that for?





Next up, there is a small speaker (or something that looks like a speaker) on the right side of the vehicle right next to the front passenger seat, kinda behind its seatbelt. What is that for?


And finally, there is a cubby under the steering wheel. What is that for?


Oh, actually one more. At the very back of the rear deck are a couple of vents grills. At first I thought they were speaker grills of some sort, but there is nothing behind them in the trunk. Are these to let the sound from the subwoofer in, or to let air out, or what?