you get glass-fibre roof linings which have a radio pod/ speaker points in them, there was a thread not long ago about them with the link to the site. some italian company makes them.
i'v got them in a S3, look quite good but rattle like fook on bumps, i was goin to take them out and fit carpet instead, cos i love that smelly old carpet smell, and it dampens all the other rattles/engine grumble while keepin more heat it!!