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

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.

At minimum, I would get a 700 watt+ power supply and a gold one at that.  The gold means it will last much longer than traditional ps.  A SSD will be much faster and won’t have to be constantly searching like a mechanical drive would. It will make no difference to the sound.  I have both in my PC and there is no difference in sound quality, it is only the speed difference. 

@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.

Thank you both, very useful information!

Unfortunately, some recent unfriendly financial events are severely limiting my budget for the time being (and for the foreseeable future). So the upgrade path suggested by @sns is not possible in my case. Luckily, I'm quite content with the sound of my system as it is. On the other hand, I'm very much aware that "everything matters" from the sound quality point of view, to a degree that many would deem ridiculous if I were to share some of my experiences, so I wouldn't cheap out on the computer / streamer side of the equation if it were by me.

I must admit though that the Lumin experience kinda killed my interest in a moderately expensive (2000-3000 euro) streamer anyway. I don't understand why the Lumin didn't destroy my PC in terms of sound quality. Also, a friend of mine has bought a Sotm streamer with the dedicated Sotm power supply and, well, it is nice but not groundbreaking if you're asking me (never heard it in my system).

I have tried the free version of Fidelizer today. I recognize it as a clear improvement, objectively speaking, but the tonal change (stronger upper bass) was not very welcome in my system. It's just not a good synergy to my current system (and taste, after all). By contrast, I didn't like Audirvana.

Btw, I have found that synergy trumps "objective" quality most of the time, and to a degree I wouldn't have though possible.

Get a Sonore OpticalRendu and connect the fibre to a network switch with the option for fibre. The rendu | power supply | USB cable can be obtained for under $2K. If you want a bit more improvement, get a FMC from the network switch to the FMC via RJ45, then to the OpticalRendu via fibre. I use the EtherRegen in reverse order as an FMC.

With what I have suggested you can use a noisy cheap computer to serve your music. I use ROON Core for this on the cheap computer. The computer is a few rooms away from the music systems. I believe what I suggested would work for non-ROON users too because the Rendu's support multiple protocols. Not just ROON RATT..

BTW - I am getting a Lumin X1 delivered soon. I doubt the X1's fibre streaming is better than the Sonore OpticalRendu, it should be similar. I only bought the X1 for the fibre streaming and to have a lower box count.