Would the I3 be a clear upgrade to the Diamond?
I still really enjoy my Diamonds a lot, heard the I3 has also nice subbass so it caught my attention.
They are qutie different like oranges to apples due to the different transducer types - single DD vs tribid with planar.
The TRI I3 is much harder to drive due to the planars inside, and sounds meh from a low powered source. So if you don't have a powerful source on hand, best to consider something else. TRI I3 is less V shaped (more of a U shape), and TRI I3 has thicker and lusher mids when amped. I think the Diamond is still bassier than the TRI I3 by a tinge, but TRI I3 beats the Diamond in soundstage when amped. Timbre is perhaps better on the Diamond. For imaging, instrument separation and details I think the TRI I3 wins here.