Stereo in Coupe GT

[gt6493c@prism.gatech.edu (gt6493c FLUHR,ERIC J)]

Thanks to all the people who answered my question about where
responses to this mailing list go.

And now while the subject of radios is up, I was wondering if anyone
had any experience with replacing the rear deck speaker in an
Audi Coupe or Coupe GT.  Right now I have small 4" Polk audios
that just don't cut it.  Unfortunately you cannot get much bigger
than that, due to the unusual design.  
Has anyone added plate-mount speakers?  Did you cut the metal section
underneath?  
I was thinking about making some sort of adapter that would raise a speaker
an inch or two above the deck, so it would fit.  Does this mess
up the sound?
Any advice is appreciated.  Anyone who knows these cars knows that sound
system upgrading is not easy.
Thanks,
Eric