Not at all, Jim. I was actually concerned about you having to wade through that rather large post of mine during a busy Xmas Eve
Playing music stored on a computer on your existing HiFi system is actually quite a straight forward in principle. There are actually two main ways of achieving it: either by direct connection or by use of a computer network. Arguably, the sound quality you can achieve from both methods is about the same, so what it really comes down to is convenience. Both methods require the use of a digital to analogue converter (DAC), which effectively converts the digital music signal produced by playing the digital files, into the analogue one that can be passed to one of the standard line level inputs of a traditional stereo amplifier.
With a direct connection, the computer is connected to the rest of the music system by a relatively short cable. In effect it becomes another component of the traditional HiFi stack. Music playing software is run on the computer and it allows you to select and playback the music files stored on the computer. The computer's own internal DAC could be used to convert the digital music signal being produced by the player software, to an analogue one and then sent via a direct connection to the stereo amplifier's line input. However, it is not usually considered to be of high enough quality, so an external DAC is normally used instead. The computer can be connected to the external DAC by various output sockets: standard USB, optical and/or coaxial digtal audio outputs from its soundcard. The external DAC device's analogue output is then connected to the amplifier's line-in. The Pioneer N-50 can be used for this purpose, as part of its function is to be an external DAC.
The actual music files themselves are usually managed by music library software also running on the computer. It makes the selection of the music files very straight forward, as it presents the files in different music categories with various ways of filtering and searching the tracks for ease of access. Quite often the music player and the music library are combined into the one application, as is the case with iTunes.
With the network connection, the computer does not need to located anywhere near the rest of the music system and if a WiFi network is used, it doesn't even have to be physically connected to it by (network) cable. The music playing software is not run on the computer, but instead on a specialised computer type device - the network audio player aka streamer aka renderer. It is the network audio player that is used as another component of the traditional HiFi stack, not the computer containing the music files. The streamer's analogue output is then normally directly connected to the amplifier's line input, as its own internal DAC is of decent enough quality so no external DAC device is usually required. The Pioneer N-50 can be used as a streamer as it's second main function is that of a network audio player. Note that the software running on specialised computer type boxes is normally given the name firmware, as it's usually more permanent ('firm') than a more 'normal' computer's software which a user can more easily install, remove, update, etc.
In a UPnP/DLNA supporting network music player, the required music files are streamed to it over the network from the computer containing the music files and running the music library software, known as the UPnP/DLNA server. Notice that unlike the direct connection method, the music library and music player are seperate applications and are in fact running on completely different devices on the network.
I could go on, but that's likely to be more than enough for anyone relatively new to this sort of thing to take in one hit!
Hopefully, you can now see why the N-50's Dig in USB can only really be used with a computer, and why "It's unlikely you'll find any router that'll be able to use the N-50 Dig in USB / async USB DAC input". It's only designed for the direct connection method to a computer I outlined above, with the N-50 being used as its tethered external DAC which in turn is connected to the rest of the music system. You can try it with any music playing software on your Mac, including iTunes. Unfortunately I'm only familiar with Windows computers and know very little about Macs. However, I'd guess, once you've connected the N-50 to the Mac with a USB cable (A to B type, aka USB printer cable), you'll be able to select the N-50 as the device to use for sound output in the Mac's system settings (ie instead of the Mac's own soundcard).
As far as using the N-50 as a network audio player / streamer / renderer is concerned, so that the N-50 (and not the computer) is connected to the HiFi, you are quite right to be wary about your router's support of UPnP/DLNA streaming, especially with regards to its ability to handle multicast data. However I would at least test it out first, if that's going to be your main reason for getting a different one. You've already said that you are able to network stream via AirPlay from your Mac to the N-50, which also requires multicast support from the router. Having said that, a worrying sign would be the N-50 occasionaly not being seen as an AirPlay device.
I understand now what you mean by klunky in that you are referring to using the Pioneer's remote control/buttons on the box and the N-50's rather small display. I thought you were talking about about using the Pioneer ControlApp for iOS & Android mobile devices, which admittedly is just another remote control for the N-50, so would be just as klunky to use in terms of navigating the various menu options. However, at least you don't have to be near the N-50 to use it, since you're using the mobile device's screen, rather than the N-50's. Do you have access to an Android or Apple iOS mobile device?
To be able to network stream the music files stored on your Mac, you need to have a UPnP/DLNA server running on it to take care of the music library. Unlike the current versions of Windows, I don't think the Mac OS X comes with one built-in (the Window's one isn't very good for music, BTW), so you have to install one. Also, iTunes doesn't support UPnP/DLNA, so its music library cannot be seen by the N-50. However, the music files stored by iTunes on the Mac will be accessable by a UPnP/DLNA server running on the Mac. Hence, it will be able to build and maintain it's own music library with the same music files and make them available to the N-50.
You did mention that the "Music Server" function was working on the N-50. Does that mean you've actually got a UPnP/DLNA server running on the Mac and are able to access its music library to play some files? If so, which UPnP/DLNA server is it? If not, a really decent free UPnP/DLNA server to try would be MinimServer, available here for download to Mac OS X (as well as other computers & network devices):http://minimserver.com/downloads/index.html
I hope this has clarified a few things and not confused you too much!
JohnEdited by Cebolla - 12/27/13 at 12:26pm