Rep Power: 186

Ok I have a 2006 Honda Civic Lx 4dr.
I plan on doing something with the rear deck, and was exploring some options. My eventual plan was to build a custom deck that will fit my 2 6x9s and somehow an 8 inch subwoofer(To pick up the mid bass better than my 2 12"s)

The 6x9s I wanted to build boxes for, which would attach to a custom made wooden panel carpeted with the same color carpet as my car has.
My questions:

I know the Si's have a built in subwoofer, and from what I can tell it actually is on the rear deck. My lx doesn't have a hole in the middle of the metal under the plastic deck, is there any way to swap my metal with an Si's? How complicated would that be...simple un-bolt-swap-rebolt...or would there be a lot more to it?

Is there any way I can get the actual carpeting that matches my car, or will I need to find a place that sells a color that is "close enough" ?(My interior color is ivory)

Is there any place online that has a schematic diagram of the back seat area/rear deck? I have access to AutoCAD and some sophisticated wood-working equipment at a friend's shop...I could take the measurements myself, but a schematic would be a lot more accurate and make my life easier.

Thanks ahead of time for any info.