I have the above setup in one system and I also have a Lumin U1 streamer in my main system. The upgrades to DAC amp and speakers are so much more bang for the buck then the small improvement in sound by spending $5k more on U1 streamer...don’t get me wrong it is a great streamer but it was the last component I upgraded. I was shocked and surprised at how good the Raspberry Pi sounds into a good DAC (USB connection - no hat). Everything I read and see online says buy a streamer costing thousands.
I picked up a Bryston BDP Pi for like $500 used. It’s based on the Raspberry Pi. Then invested ~$1K for a Small Green Computer to host the Roon Core. Then switched the Pi to Roon Endpoint. Dolled it all up with some decent cabling and Mesh network. I am amazed at how good it sounds. I would like to someday switch to optical rendu endpoint.
I agree: spend the rest of the budget on good cables, network infrastructure and DAC.