@unclewilbur - Below is a basic overview. At your price points, I recommend looking at these guys for reasonably priced servers and streamers. Their support is good and their servers are configured to directly rip/upload your CDs when connected to the server via a CD drive.
- Modem: Inputs the internet signal coming into your house by cable or fiber and sends it by cable to your router.
- Router: Sends the digital internet signal to devices in your home that need internet service, either wirelessly or by cable or fiber.
- Server: Stores and catalogs your digital music files, usually on an internal solid state drive within the server, and provides an interface for managing your music library including downloads from a streaming service. If you use Roon as the gatekeeper for your digital music then the server operates what is called Roon core or Roon server.
- Streamer: Connects to your home network or internet via Ethernet or Wi-Fi and inputs digital audio from the music server, online streaming services, and/or internet radio, processes and reclocks the digital audio signal, and then sends it to your audio system’s DAC. When using Roon, the streamer has the role of "Roon endpoint", which is a separate function from Roon core or Roon server.
- Server and streamer can be in one box or separated into two boxes. Mine are now two separate components and while I do not hear noticable differences in servers, I definately hear differences between different streamers.
- DAC: Digital-to-Analog Converter that inputs a digital signal, converts it to an analog signal that is output in left/right channels to your preamplifier or directly to your DAC.
- Which DAC: To answer this part of your question, there are more than a few folks who seem to like the Laiv Harmony DAC at less than $3K, but there are many others you can look at. There are DACs by Gustard, Topping, and Benchmark for under $2K that measure quite well and seem to satisfy many. If you can get to $4-5K, then maybe LTA Aero or Mojo Audio Mystique Y. With a little more to spend, up at about $10K, look at Mojo Audio Mystique X SE or Merason DAC1 MkII. There are other worthy candidates at all those price points too.