Hi,
Other than a desire to audition streamers before purchase and Roon use, you didn't provide a lot of other information as to what your requirements are. It seems like you don't need an internal dac with your streamer. Are you limiting the choice of USB for any particular reason?
Both the Auralic and Lumin devices will be a lot more expensive than the Element S, especially if you want to buy the external power supply for the Auralic which will add around $1000. As far as I know (and I could be wrong) the Auralic streamer is not yet Roon Ready.
There are other options that will cost you less, including the new Volumio Rivo Plus and the Mano Ultra mkiii.5 Farad both of which may be tried out and returned. Rivo+ is Roon Ready, and Mano Ultra can be configured as a Roon bridge.
I have both the Element S and original Rivo, and enjoy both streamers very much. They both work flawlessly with Roon and are both Roon Ready.
There is also the Holo Audio Red streamer that is around $1000 and has received a lot of positive reviews. I use the Red wih my Holo Audio May dac and it works flawlessly, and is also Roon Ready.
Let us know which device you end up choosing.
Cheers!