The Pioneer VSX-828 is already a UPnP/DLNA supporting streamer, so there should be no need to get another one!
Your problem is that you're attaching your USB HDD to the wrong box on the network, if you want to use a UPnP controller app on your mobile phone. The USB HDD needs to be attached to a networked device that has a UPnP/DLNA AV media server application on it, such as a computer or a NAS.
Your Pioneer does not have a UPnP/DLNA media server, exactly like the vast majority of other UPnP/DLNA streamers including the Marantz NA stereo streamer models you mentioned, so you'd have the same problem with them.
Like I mentioned in your other thread, you could use a WD My Cloud NAS, as that has a UPnP/DLNA media server and you can attach your USB HDD to the My Cloud. However, I would not recommend it, because some have reported the My Cloud's TwonkyMedia server to do odd things with music files: like order them alphabetically by name instead of by track number - not much use if you want to play an album's music tracks in the right order.
My recommendation would be to instead use a decent music file dedicated UPnP/DLNA media server, such as the excellent MinimServer. You can install MinimServer on a computer and on some makes of NAS, such as Synology & QNAP, but unfortunately
not on WD NASs (eg My Cloud).
However, if do want a good cheap solution and are ok to to a bit of DIY, you can even install MinimServer on a tiny cheap reliable low powered computer such as the Raspberry Pi 3 (~£50 inc case & power supply). You can turn it into a 'NAS', by attaching your USB HDD to it and save money (~£50+) by not having to get a ready made NAS:
Installing MinimServer on the Raspberry Pi
By the way, what UPnP/DLNA controller app are you using for your phone?
If it's an Android phone, my recommendation would be the BubbleUPnP app.