So you don't think getting a " higher quality " motherboard and codec is the way to go.
Correct. Processing speed is no problem, you can play HD audio with an RPi these days.
Internally a sound card or a USB audio interface (DAC) both offer codecs. LE will select the best one, and transforms from source to target. For stereo, the sampling rate is the most important spec of the codec. The above Behringer UMC22 offers 48kHz sampling rate, but you can go higher with a better audio interface.
Because audio interfaces for musicians have high sampling rates, low latency and best analog connectivity (balanced output), an audio interface with studio speakers (balanced input) is the best stereo setup you can buy.