Inexpensive but good sounding power supply (and hard drive) for PC audio?

@stereo5 Not my experience with mac minis, I used hdd and ssd via sata drives and PCIe ssd in various extremely modded minis, sound quality definitely impacted. I'd expect same in Windows computer. My present  Windows custom build streamer runs OS in ramroot, runs OS off RAM, this better than any ssd.

When streaming via my home theater setup I always use Wasapi Exclusive, better than the other schemes I've used.

For sure adding external power supplies to Windows based server can be problematic in how to run external cables. I had to cut out top panel of streamer to be able to fit the JCAT Optimo S ATX lps cabling to motherboard.

I suspect many won't take you seriously with idea of using your computer as high quality streaming source.

I ran various modified mac minis for years and presently use Windows based custom build at present. While my custom build has virtually nothing in common with a general build Windows machine, I do believe one can create a decent streamer with certain mods to general service Windows machine.

I doubt more than minimal improvements with power supplies you mentioned, much better would be HDPlex optimized SMPS allied with external LPS HDPlex 200W dc-atx cost around $70, sufficient lps to power HDPLex will be $400 up.

Assuming you have sata drive, ssd will be nice improvement over HDD.

JCAT or Pink Faun usb card would be substantial improvement over any other usb card or usb off motherboard, a little pricey but worth it!

Optimizing your OS is another substantial improvement you could make, something like Windows optimizer, I use Euphony OS. Be aware these OS modifications will severely restrict or eliminate use of your computer for general service needs

I believe this is minimum for what I'd do for modifying general service Windows  machine into music streamer. Without all three of these changes you'd be greatly limiting potential of this machine for music streaming duty. You could do any one or two in isolation with incremental improvements, but not really worth the effort or expense.

As for total costs here, think $500-$1500 for power supply via HDPLex route, ssd could be anywhere from $75 to multiples of $100, one could have OS only on ssd, storage on HDD or everything on ssd. Nice usb card around $800, Windows optimization could be anything from diy for free to subscription to Euphony or another OS for  $200 up per year. So bottom line cost here could be as low as something less than $2k-over $3k.  Weight this against what an off the shelf would cost, come to your own conclusion. Keep in mind to reach this level the Windows computer can no longer be used for general purpose. If still needed for general purpose you'd be better off going with dedicated off the shelf streamer. Eliminating the many processes Windows general service computers running is absolutely necessary to hearing potential of the other mods.

I go into this much detail because this is exact place I was at some months ago in determining whether I was going to go with diy mods to Windows based computer or off the shelf. In my case this was all out assault, so comparative purchasing decision  was to machines like Antipodes K50, Innuos Statement, Aurender W20SE. I chose extreme custom build Windows based mostly because I'm the type that loves bespoke solutions. Whatever route you take, I'd not cheap out, based on your system description, I'd expect you'll hear the improvements brought from a top quality streamer.

@agisthos Euphony OS for Windows eliminates any use of Windows as computer, all you get is BIOS screens and Euphony screen. With I9 processor using less than 3% on only two cores in server mode handing off to Sonore OpticalRendu for streamer. Euphony OS integrated with Stylus music player software for seamless user interface.

I too thought Windows machines would have entered plug n play market, Baetis is only company I'm aware of offering music streamer using Windows platform. Based on individuals I'm acquainted with over at Audiophilestyle forum it seems diy crowd  can build streamers that can beat all the plug n play streamers with exception of Taiko Extreme, perhaps Wadax. The builder of my custom streamer and subsequent owner both compared this build to some of the best plug n play, this preferred until comparison to Taiko Extreme, which both purchased. At time of their comparisons this build running HDPlex, I'm running with JCAT Optimo S ATX. Wonder how this would compare now?

I doubt profit margins using fully optimized Windows hardware and OS would be nearly as great as the Linux based. Comparing internal parts cost in my custom build vs what I see in most plug n play is no contest, mine far above. Add in $6k Optimo LPS and nice case needed for plug n play market, it would probably have retail cost of Taiko or Wadax, and still may not be as good considering all the proprietary technology in those two streamers.

@auxinput That is correct, Euphony Version 4 is reportedly big upgrade on 3, never had 3 so can't say.

I'd agree quality power supply may not make that great a difference with Windows computer, the Windows based motherboard music server I'm running is in actuality not a computer, has virtually no capability of a general service computer. At this level of minimal processing and hand picked parts chosen for lowest possible noise, latency, power supplies make large difference!