The DP-X1A has 4 different gain levels (Low 1, Low 2, Normal and High) - for the T1.2 (600 Ω) I set it to "high" (when listening with a balanced 2,5 mm cable with my UE TF10 I have to set it to "Low 1" or "Low 2").
As volume is a subjective thing and soundfiles differ from their - let's call it "native" volume of the files - I try to illustrate with Tidal (HiFi) as I believe everyone should have quick access to the referred tracks. I set the volume throughout listening and will post the volume I found "nice" for that kind of music.
1. Jesse Sykes & The Sweet Hereafter - Sunday Skin (from: Gentleness of Nothing) - Volume set to 120/160 - relaxed folk rock
2. Popa Chubby - Hey Joe (from: The Essential Popa Chubby) - Volume set to 127/160
3. Wolfgang Haffner feat. Max Mutzke (from: King of Cool) - Volume set to 127/160 - smooth Jazz
4. Jonas Alaska - Becky (from: Younger) - Volume set to 140/160 - love the sound of the fingers sliding over the strings of the guitar - great recording, superior quality (thank you Tidal)
5. Izzy Bizu - White Tiger (from: A Moment of Madness) - 140/160
Going over 150/160 it becomes to loud - at least for my ears. With the T1.2 I'm basically listening in the range 100 - 140.
From my perspective the DP-X1A plays very well with the T1.2 - no need to amplify. Loud enough. Absolute beautiful highs, mids and bass. I honestly never enjoyed music this way on a portable device.
To me your volumes would be loud. I listen to Tidal hifi with the gain at normal and I never go over 110, this however is with my Alclair RSM CIEMs. Beautiful pairing!