I preferred the U2 i demoed over the Aurender A10 i had ($6k), the Aurender was a disappointment in my system, and that app is just acceptable at best.
The U2 was more lively, detailed and over all felt like music more. the A10 was just boring ( not the same as the ones your looking at but all i have to go on). I use an external DAC and I recommend this route as well the DAC is the most important part is this chain and will effect the sound the most IMO, so do not lock yourself into an internal DAC in a streamer.
Yes I'm not an Aurender fan after owning the A10 I don't think I could bring myself to buy another. They are nice looking but performance was not what I expected for the price new. Oh you need an apple tablet to operate it as well, a phone works as a remote but you cannot set them up on the phone only the tablet. potentially they have changed this now.