@samzx12 I've used both USB and SPDIF on my U2 mini.
USB was quieter, but that was probably due to the TotalDac Gigafilter cable filtering out the noise.
Get a Berkeley alpha USB interface series 2 for the U2 and that will be the end game setup.
It isolates the USB port from the reclocked digital signal.
It will be a huge leap from the USB/SPDIF output of the U2.