>>105688907 (OP)Here's what I suggest. And this is just my experience.
Buy a used home theater amplifier - usually called an "av reciever", ~45-60$ but just use it for audio. These are good enough amps for hifi and people set the price low because they are shit for video these days. I use a sony str dg520 I got for free. Very old amps (think 70s/80s) can have blown components, so I wouldn't trust anything super vintage without testing.
Look for used passive hifi speakers in your area and just do some due diligence on the quality - look them up. I found some polk bookshelf ones for 80$. You'll need some thick speaker cable (e.g., 12-16 AWG) to connect it to the receiver. Don't do more than a stereo pair of speakers. Don't do powered speakers, as there's no joy.
EITHER - get an external DAC, and plug it into this amplifier. OR get a high quality 3.5mm cable and run from the PC.
DO NOT SKIMP ON CONNECTORS. 3.5mm/RCA cables, splitters, adapters, tend to be weak links in practice, and degrade sound.
If your onboard motherboard audio is bad you usually hear it as a low constant hum or crackling. That's when things are not 'shielded'. Don't expect to hear higher quality audio from an external DAC unless you hear an obvious problem in your existing audio setup. Are there weird noises? Does it sound worse as it gets louder or quieter?