What is the added value of a streamer over a networked dedicated Computer

I think two important things to consider are what have you invested so far in your current platform (time, not money) and how do you plan to use the streamer. Personally, I prefer physical media. Nobody can take it away from me and having gone on an audio hiatus, the ability to come back and pick up where you left off is invaluable. So for me, I rip CDs and convert 78’s, 45’s, and LPs to DSD. I have about 10k pieces of physical media - been collecting since I was 12. About 40% of my collection is converted. I rate all of my songs and have it scaled down to about 45 days of 4-5 star songs. When I’m feeling lazy or preoccupied, I go digital and hit random. This is home, work and car. That’s about 270 days of listening for 4 hours a day without repeats. If I want quality, I go back to the originals. I have invested a lot of time in JRiver as my program of choice and it carries my organization when they can’t be embedded. If this was my only transport, I would feel differently. With a dedicated PC, a personal collection vast enough for me to forget a song exists between plays, and a good DAC, I don’t long for more. Since convenience is the attribute that separates my digital from my physical media, the idea of fiddling with 1 and 0s is not appealing to me.
The same could be said by some about analog. I’m comfortable with a meter, a control screwdriver and a magnifying headlamp. Others may be comfortable with a program. Me, when I have a digital issue, I end up somewhere on the dark web downloading a troubleshooting program. Now I believe a streamer (and based on what I read in threads like this - lots of other parts I just don’t understand) could improve my sound. However, with years already invested in my current process, it’s not worth it for me. This is largely because of how I use it. I often hear things like - great streamer, but the interface is just OK. In my opinion, the interface IS the streamer. If that’s clunky, where’s the benefit over physical media. And if that doesn’t pick up your current catalog and preserve the work you have done so far, don’t bother. 

Other than the fact that a dedicated streamer can be as good (and expensive) as you might desire, all of the factors are similar. You have one advantage of with a computer you can utilize it for other uses at the same time, but that is a trade-off because you must have the computer turned on to stream with even if you are NOT using it for other things and the computer probably draws more juice out of the wall just sitting there humming along. HTne with the computer you have access to just about everything that is available. there are a lot of things that a dedicated streamer can't access.

Relatively easy to understand optimal input on dacs, not so easy with the computers serving dac. First off, servers and streamers both computers, and it is the rendering service they provide that makes all the difference in obtaining maximum potential from dacs and streaming chains. Servers or one computer setups may or may not provide optimized rendering, many run rendering ports directly off motherboards, not good since these motherboards must run many processes allied to music players and OS, the more processes run the more noise produced, not good. The streamer has very little to do in comparison to server, motherboard runs very elemental OS, with focus on rendering, which means nice power supply and good clock. Servers very rarely provide this level of rendering, the few that do are easily $10k plus.

Get a nice streamer, server becomes much less important, not saying still not important, only less. In order of importance, dac, rendering, server, network.

There is one other way around two computer setup, streaming dac. Assuming quality rendering within dac one only needs to concern oneself with server.

I'd agree with those stating general service computer doesn't belong in quality streaming setup. There are means and paths to go diy through self builds and modifications of off the shelf GS computers, but one needs computer savvy. Add up time spent gaining knowledge, actually performing mods, expertise to carry out those mods, parts needed for these mods, Nope, vast majority better off getting off the shelf servers/streamers.

I started streaming using a higher-end Dell laptop, USB to the DAC.  I upgraded to a Roon Nucleus Plus server and the USB port is much quieter than the one on the Dell and the server maintains its self with no work on my end (other than responding "yes" when prompted to install software upgrades).  The sound quality is much better from the Roon server.

If you haven't done this already I would suggest that you compare a streamed album with one that you have ripped in FLAC. See if there's any difference in sound using your current setup.

In my case I have ripped my CD library (over 4k titles) into uncompressed FLAC but I still have all my CDs. I am streaming through an ASUS gaming laptop (I7 processesor) into the USB input of my PS Audio PerfectWave Mk II DAC. Note that the DAC has a "Digital Lens" feature that buffers and reclocks the data which should take care of any digital hash from the laptop. I also use Qobuz.

I have compared several CDs with the FLAC ripped version as well as the same version on Qobuz - all through the same DAC. The CDs go through my PSA PerfectWave Transport. I can't hear the difference between the three formats. They sound identical, or at least similar enough to not make a practical difference.

I wouldn't expect a FLAC version of one of my CDs to sound better than the CD itself. Using this criteria I can't see how an expensive dedicated streamer will help me. The other advantage of using a PC is that it can serve as the Roon core when I go with Roon at some point in the near future. BTW, the Qobuz version sounds the same as the other two formats which is to say that they all sound very good.

To put this another way, is anyone saying that a FLAC played through an expensive streamer actually sounds better than the corresponding CD played through the same DAC? If so, that is a demonstration I would really like to hear.

I read folks saying that an expensive streamer sounds way better than a cheaper option but I never see them using any sort of reference to help pin down the differences. I really think that you have to compare against a reference to get an accurate picture of how much difference there really is.