The Moondrop Aria 2 is 33Ω at 107.2 dB/mW; the Moondrop KATO is 32Ω at 108.1 dB/mW. This page is only about what they ask of an amplifier — not how they sound, which no specification on either sheet can tell you.
The Aria 2 needs 0.9 dB more than the KATO to reach the same loudness — 0.19 mW against 0.15 mW.
| Specification | Aria 2 | KATO |
|---|---|---|
| Impedance | 33 Ω | 32 Ω |
| Sensitivity | 107.2 dB/mW | 108.1 dB/mW |
| Sensitivity (voltage) | 122.0 dB/V | 123.0 dB/V |
| Power for 100 dB | 0.19 mW | 0.15 mW |
| Voltage for 100 dB | 79 mV | 70 mV |
| Current for 100 dB | 2.4 mA | 2.2 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 4.12 Ω | 4.00 Ω |
| Sources that reach 100 dB out of 280 | 280 | 280 |
Every source in the database that drives one of them drives the other. On power, the choice between these two changes nothing about what amplifier you need.
1 source stays below the audible-hiss threshold with the Aria 2 but crosses it with the KATO (FiiO K11 R2R).
280 of the 280 sources here reach 100 dB on both. That count is about power only — the output-impedance and hiss lines above are separate questions, and a source can pass this one and fail those.
Each model has a page of its own with the full source list, the hiss estimate and the provenance of every figure above: Moondrop Aria 2 and Moondrop KATO. Every figure on this page comes from what Moondrop published, or is derived from it — what that maker publishes, counted.