Tim,
Putting in the Premium speakers is a no-brainer.
As for the 3rd light, the problem, IIRC from one of Tim's cars, was the fact that the sunshade interferes with a large brake light housing. This is the case with the BMW OE one. So, you may need to find another brake light assembly there, and one with a stand of some sort to be able to mount it to the shelf (bolt or screws), and have it face flush against the rear window.
The one on Tim's car was glued to the window.
On my car, which originally came with the euro parcel shelf without a sunshade, they simply screwed the US 3rd lamp assembly to the shelf. It wasn't flush with the rear window, so every time I braked at night, I could see the reflection in the bottom portion of the rear window. Very annoying.
A quick search turned this up:
http://www.jcwhitney.com/autoparts/Prod ... 01/c-10101
but it's a stick-on.
You probably will find better luck trying to find a slim, LED style brake light, which will be almost guaranteed to fit without a problem.
I know someone on the old Welty Digest (late 90s) actually cut a block of wood to act as a stand, and then screwed the brake light to that, and then to the shelf, rather than buying the US shelf.
-Chris
