Multichannel DACs / ADCs ?

I have been using some dirt cheap 2x8 (2 in, 8 out) USB soundcards for a while with Volumio to implement active crossovers.

So far, PCIE soundcard performance on an x86 system has been much better (than USB on the arm7). No surprise there, but I’d like to close the gap a bit.

It’s possible that a better USB soundcard could improve things (Asus Xonar) on the RPi2 … but I wanted to see if any of you had experience with multichannel I/O via the GPIO (i2s).

So, anyone using more I/O than just stereo output?