Not exactly sure what's going to happen, but can I ask why you specifically want the vali output back into the aune t1? Just catching up with this thread, but I don't really see what's so bad about just using the vali out. Sorry, if I missed some information that you posted earlier.
A thought just crossed my mind:
If I get a more demanding headphone in the future, what happens if I use the amp to feed another amp. Will I get more power to feed the so-called power-hungry cans?
This is my solution: Line out into another amp. Works perfectly.