I have a Bluesound Vault 2i and it's been great . It's probably at least 6 years old now. I use it everyday. Several times a day.
When that dies I'll probably buy the Icon.
I did have a demo of the WiIM Ultra and I thought it sounded pretty good
You're buying into an Eco System that's driven by both the hardware manufacturer and the streaming platforms. I recommend Blusound because they have been doing it a long time and it's a solid platform. Lenbrook , parent of NAD, Bluesound, PSB, etc has huge resources. Cyrus and Roksan have both adopted the Bluesound OS for their streamers , among others.
Yes Aurender makes great machines. If you look at it from a build quality, sound quality, support prospective it's a good value, but only if your associated equipment warrants the cost. I have a N200 but I use my second system with the Vault a lot more. The Vault may not be as good but it's a much better value in the true sense of the word.
If i was looking for a sub $500 streamer I would buy a Bluesound Nano or a WiiM. End of story.