Raspberry Pi 4 to Lumin U1/U2 Mini

Currently running a few Raspberry Pi4 (w/LPS) with Ropieee, planning to get a U2 mini.
Would the sound quality be big improvement or just a marginal better.

In all honesty, I think you’d be wasting your money. Streamers deliver digital data to the DAC for onward conversion to analogue. They have no impact on sound quality.

I ran an experiment this week - I played a -120dBFS 1 kHz square wave tone from Roon via my PoE+ powered RPi (SMPS) into my rig (Benchmark DAC3 HGC/HPA4/bridged mono AHB2s). At 0 dB on the HPA4, I could hear silence, at +4 dB on the HPA4 I could hear the 1 kHz tone. With the right gear, a RPi is capable of delivering a discernably audible test tone out of a -120 dBFS signal. If you combined that test tone with a music track, even at ear bleeding noise levels of music playback, the test tone would still be below the threshold of audibility.

Save your money.

This gonna be good.