Unfortunately, I don't know of any other good headphone stores in Switzerland beyond the ones that I listed. If you don’t live near Zurich, I suggest that you take a look at the Sennheiser HD 800 Authorized Dealer List to find a store closer to you (the list features shops throughout Switzerland: in Geneva, Basel, Lugano, etc.): http://www.sennheiser.ch/consumer-hi-fi/kopfhoerer/hd-800/ Not all of the stores on this list are great, but almost all of them sell a number of other brands in addition to Sennheiser, as well as of course other headphones made by Sennheiser. Importantly, most of these stores also allow you to audition any gear that you're interested in.
Yeah, the store in lugano is in front of the university campus, I already went there; turns out he only sells Sennheiser and Bose, mostly Bose, and when I asked him about headphone amps he made a funny face. He only sells speaker amps. To think he sells HD800 too is surprising! How does he expect his costumers to drive them?
BTW, I dont blame him: he has a really small place, plus I have the impression there's not much demand for audio-quality here in Ticino... I hope that maybe Monster's marketing can convince them spending 100$+ on headphones isnt madness... I think in the long run even others manufacturer will benefit from this.