"Could it be that the DAC in the streamer is better than what you used when using a computer as file source?"
I have owned multiple streamers, from folks like Metrum, Antipodes, Sonore, Mojo Audio, and Small Green Computer, and some of those were server/streamers, but I have never owned a streamer/DAC combination. The combination of a DAC within a streamer, or server/streamer, is not unheard of but also not common with the equipment used by most on this forum.
There is a lot to unpack here, and the OP should really do more research on this site, as well as looking at offerings by manufacturers, just to see what is out there. If they need file storage, then they may need a server since many streamers do not offer storage. If they want to run Roon, they will need something to operate Roon Core. A computer will do those things, as will a server, but not all streamers. So, questions include:
- do they need storage for their own music files or do they simply want to stream from the internet,
- how do they plan to interface with their music, i.e., using Roon, or other platforms,
- is this a first step toward an overall digital playback system that they intend to grow, or are they looking for a one and done solution, and
- what is their budget and time frame?
There is no roadmap for exactly how to get there but it does help to start with the end in mind.

