Unless you hear interference (static noise/transients) then speakers and room acoustics are more likely to be lot bigger sound quality bottleneck.
Normally I would agree with this, however the on-board on the Z370 is shocking.
The sound is not even linear, really thin, then adding in bunch of interference.
It's not even up to 80's cassette players.
I'm not talking something not quite as good, or this is a little better then this, i'm talking go to a car boot, pick up a £5 Amstrad CD player from the 80's, the the £5 car boot special will be better.
If the Gigazyte Z370 on-board was a car, it with be a 20 year old Corsa with the bushes gone, dampers leaking and mismatched tyres!
One of these days i'm going to feed the motherboard audio into a high end DAC, then A / B it with another source, so everyone can hear it, then stick it on YouTube.