The Universe leather pads are what made me fall in love with the Atrium. I experience this combo as what music sounds like in a live setting, especially vocal-focused and natural instrument music. For 90s alt rock, singer-songwriter, folk, doom metal, and other genres where voice, drums, guitar all matter the most, this is my config. Analog, organic timbre. Mid range is magical and REAL. Mid bass is powerful and kick drum (all drums really) are felt and sound like you’re in the room with them. Treble has a downward slope but there is plenty of air and stage.
The Caldera ultra-perf pads do a couple things for me. Namely they balance out the overall sound and speed everything up in terms of decay, reverb, resonance. You lose some of the mid-range magic and a bit of mid-bass (but not much), but you gain more even and extended treble and air, even wider soundstage, and significantly perceived sense of speed. I use this combo for modern metal, especially really fast stuff, and anything inorganic like electronic beat backed stuff ( a lot of Bjork, honestly).