Continuing from above, I already said in my OP that I don’t really listen to internet streaming (eg Spotify, or higher resolution internet sources) for serious listening. I appreciate the massive expansion in listening choice they offer but still prefer to have local "hard copy" and listen to that rather than be at the mercy of internet connection for uninterrupted/uncorrupted high quality audio. Perhaps my loose use of the word streamer in my question has given a different impression.
@Fuzztone re "If you had wisely spent on music reproduction equipment all of the money you handed to Apple, you would have a fine system. Details? I don’t know anyone that tricked out a Mac enough to stop there. Most stop at an Amazon Echo before they even get there."
I believe I do already have a fine system, thanks, and I gave no money directly to Apple since I bought the Mac Mini used. I did buy it as a way to get into SSD-based high resolution music files as well as convenient backup of my CD collection. That said, I remain interested in cost-effective upgrades to my system but am still unlikely to prioritise internet-streamed audio over locally stored music (or music via wifi) for serious listening in my dedicated listening room. I do send via Airplay to devices in other rooms when I’m in "party" mode but that’s not for serious listening. You (and others) asked for details. The system components are ageing but I have found that newer is often not necessarily better; furthermore earliest iterations of new technology direction have often been poor alternatives to traditional sources. My own view (open to alternative suggestions) is that the weak links in the digital chain are the 2 DACs. So my question about streamers is because I need to consider suitable interfaces/connections for digital sources/servers when upgrading the DAC, and also that I’m aware that some streamers come with an onboard DAC. I also recognise that internet-streamed audio will likely continue to improve in the future.
Analogue source: Audiomeca Romance turntable with Romeo uni-pivot arm, Van den Hul Condor Gold coil (LO) MC with suspension adjusted by vdH himself (begrudgingly!) for uni-pivot arm
Digital source 1:
Audiomeca Mephisto CD transport connected via BNC to Audiomeca Ambrosia DAC. This DAC was high end at the time of purchase but doesn’t handle high resolution audio. Nonetheless, over the years since I have auditioned other DACs and significant expense would have been required to improve on it significantly. One DAC I did demo at home which ran rings around it (but which I couldn’t afford) was a dCS Paganini.
Pre-amp: BAT VK30SE (Tube) with onboard phono stage
Power Amps: Audion Black Shadow 845 monoblocks (modified)
Loudspeakers: Coincident Super Eclipse III (92dB/14Ohm)
In addition to the above, as a weekend warrior musician, I was doing some home recording via MacBook Pro laptop and had already purchased an Edirol (Roland) multichannel USB interface for that purpose, capable of handling up to 24bit/192kHz data. This is essentially an ADC and DAC in one box with optical and MIDI in and out as well as USB. It’s connected to the preamp with audio note silver cables. When exploring high res digital audio files via the hifi, it made sense to me to begin with this device I already had. It also made sense to me at that time, if wanting to listen to such files using the hi-fi, to move from my laptop to a device not being used for other purposes and to keep those files along with my ripped (aiff) CDs on dedicated drives. Having done so, I have found the sound quality of the Audirvana/MacMini/Edirol combination remarkably good, given the price, such that I rarely listen to the original CDs. The situation is further complicated by the fact that the Edirol requires a driver and the drivers weren’t updated beyond the Mavericks OS, so the Mac Mini runs on that legacy OS and I can’t update the Mac Mini with later OS. However, since it’s dedicated to hifi listening and recording (not simultaneously), that’s not been a problem for me.
This is the context of my question on streamers, and I remain primarily concerned about the quality of handling of the music files on the drives (both the mac mini’s onboard SSD, and a couple of external drives with wired connections to the Mac Mini), as opposed to music which may be streamed from the internet. I am not expert in the technological details of rendering but was under the impression from what I read on the PS Audio website that, specifically with regard to timing issues, rendering by the computer was essentially (ahem) rendered irrelevant when playing music files from its SSD using a USB interface. Happy to be educated further by those with real expertise in this area.