For devices with a cold-device plug (which is the case with the be quiet system power 9), I would leave out the adapter and order a CH cable for it. That way you don't occupy an entire triple socket with one plug. It bothers me anyway that the online retailers don't supply a suitable cable but only the adapters. OEM mains connection cable Switzerland plug IEC socket C13 (1.50m)

Actually, no devices with foreign plugs may be sold in Switzerland. The fix adapter is permitted, but must be supplied free of charge by the seller. Only with it do 3 plugs no longer fit into the wall socket.