For 30 years, the family business Medussa has only sold materials they are passionate about. The manager, Marc Goyvaert, started his business in response to repeated demands from people impressed by the house he had had built for his family.
Their stock room, partially covered, is effectively a showroom. A visit to their (extremely detailed!) website gives an idea of their range, which is mostly top end.
Medussa only buys and sells, but they do offer advice on transport and installation. Used to international customers, they can even make your travel arrangements and organise your hotel if you are travelling a long way.