I’ll bet if the dealer carried Aurender he would change his view on what sounded best. It’s always amazing what they recommend is always the best.
I have also thought most other high end streamers sounded better than aurenders. I bought the Auralic Aries over the then top of the line Aurender. The Lumin and Lightning DS software was much better than Aurender software.
If you don’t use usb (which I haven’t since owning the Auralic), and you use Ethernet to the dac, you don’t need any special server to run Roon or Audirvana.
Since no server is better than any other server/streamer at reading bytes off a disk, the only thing you are buying a server when using usb to the dac is if the server has enhanced the usb connection.
Since I switched to i2s to the dac and my server is in a different room running Roon, I bought a streamer that gets my server data from wired Ethernet and outputs to i2s, no disks are attached. This streamer is an end point in Roon.