I have not compared T3 to Qutest but have compared the T2. This is not a fair comparison. Tonally similar. The T2 sounded much bigger than the Qutest in terms of image height and width. Qutest has the edge in terms of depth and the T2 had a small edge in terms of detail. No one I have heard is better than Chord between the speakers in terms of image depth.
All around, most people would probably be biased toward the T2/T3 but it is also a $5K unit vs a $1600 unit.
A fairer comparison would be to put the T3 up against the TT2. I think the TT2 is probably the better DAC in that scenario as It is more detailed and maintains its edge in terms of soundstage depth and the overall image is bigger. But then, it is a $5500 unit without streamer vs $5K unit with streamer so again, you would expect this.
An interesting alternative would be the Weiss 204 as it is priced in the middle at $3.5K and if you added it with your U2 Mini, it might be as good if not better than the T3. .
Full disclosure. I am a Chord and Weiss dealer. I don’t sell Lumin but have had multiple Lumin devices in on trade.