Naim Supernait vs Nait XS vs Nait 5i: Differences

I have read that the Supernait sounds close to the XS. Are there substantial sound differences between these three models? What are the expected improvements going from the Nait 5i to the XS, and the XS going to the Supernait? Apart from the additional features of an on-board DAC in the Supernait, does the unit have superior sonics compared to the Nait XS?

Any advice would be appreciated.