Not a direct comparison but I hope you can draw a correlation. A few years ago when I auditioned an O2+ODAC vs the Modi+Magni, the O2+ODAC was the cleaner sounding but the Modi+Magni was more fun and dynamic. I ended up buying the O2+ODAC.
When I compare my O2+ODAC now to my Aune T1, the T1 is more dynamic. If memory is accurate (which often is not), it's just as dynamic as the Schiit stack. There is more bass and the mid-range is much lusher.
Also like I said, the higher output impedance on the Aune, will sound much better on the HD6XX.