On the other hand the Devialet is no iDevialet or iDevice at all. So it should do its work in every WiFi environment. As there is no special Apple-WiFi ;-) I am an Apple user too and I do not have a Problem with buying a Mac Mini if necessary. But I don't want to buy another router (Airport Extreme) just for the Devialet. Everything else in our house is working well with the Fritz!Box since years. So I will try WiFi and if it does not work I may go for USB or Ethernet connection. As Devialet Said without a drop in sound quality.
You are looking a this totally wrong. To extend an existing WLAN network over WLAN there are different implementations from different companies and no real standard. For this reason this only works optimal between two apple devices or two devices of another company that implement such thing. Also a lot of routers, access points and so on from different brands do not really work reliably. This is not so obvious if no constant large data stream is needed.
Also you do not have to buy a Mac Min special for this because this is not the problem. The problem is always the network infrastructure.
An with a new Devialet that has the wired possibility this is the way to go anyway.
What I find interesting is, that you worry about quality drop when you are using cable LAN instead of WLAN.
Even when comparing SPDIF on the D-Premiere to AIR it is not always so that AIR works better because in the past AIR suffered in some firmware versions from sound degrading things.
And I can guarantee you from extensive experiments I have done, that loudspeaker slection, loudspeaker placement, room treatment (carpets, furniture and so on), power cable, loudspeaker cables have much much more influence to good sound than any connection variation on the Devialet.
And regarding loudspeaker selection: It has very little significance if a loudspeaker with the Devialet works in any dealer demonstration or not. It has to work in the own room. You only can do some preselection on the dealer site and then take different speakers home and try it in your environment because the environment has enormous influence on the way a speaker makes the sound in a room.
Everything is her connected to each other in real time and only optimizing the combination will be successful.
So it is not astonishing that often presentations of Devialet amps in combination with really good speakers do sound so terrible in demonstrations. The Devialet and good speakers are particular sensitive to their environment as they can push enormous energy in short time into the room, which the room has to handle correctly and the walls, floor, ceiling, furniture has to diffuse, absorb and to some degree to reflect.