I've traded my old amplifier for an Airport Express with Kenneth. Yesterday he also provided me with a power plug, because the Airport comes from the USA, and thus came with the wrong power plug. And I cannot seem to locate mine that came with my PowerBook, nor the one that came with Veerle's MacBook. Sadly, I seem to misplace a lot of stuff lately ;-)
Yet, the device works like a charm. I do think I am broadcasting through my Airport Base Star, instead of directly to the Express, as the former seems to be running pretty hot. Still, finally I can let the neighbours enjoy my iTunes library. I'd recommend it to everybody.