Short answer
Both are desktop amplifiers, $799 against $660.
On raw power they are level: each reaches 100 dB on 567 of the 567 non-electrostatic models here.
| Specification | Aune S17 Pro EVO | Grace Design m900 |
|---|---|---|
| Power into 32Ω | 2.0 W | 1.0 W |
| Power into 150Ω | 464 mW | 228 mW |
| Power into 300Ω | 235 mW | 115 mW |
| Power into 600Ω | 117 mW | 57 mW |
| Output impedance | 1 Ω | 0.08 Ω |
| Output noise | not published | 5.01 µV |
| Price | $799 | $660 |
| Headphones it reaches 100 dB on out of 567 | 567 | 567 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Balanced | Aune S17 Pro EVO | Grace Design m900 |
|---|---|---|
| Socket | XLR4 and 4.4mm | no separate rating |
| Power into 32Ω | 7.5 W | — |
| Power into 300Ω | 918 mW | — |
| Output impedance | 1 Ω | — |
| Output noise | not published | — |
| Headphones it reaches 100 dB on out of 567 | 567 | — |
Only the Aune S17 Pro EVO has a separate balanced rating from its maker; through it, it reaches 100 dB on 567 of the 567 models here. The Grace Design m900 may still have a balanced socket — its spec sheet simply gives no figure for one, so there is nothing to put beside it.
| Load | Aune S17 Pro EVO | Grace Design m900 |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Published | Derived |
| 300 Ω | Published | Published |
| 600 Ω | Published | Published |
Both makers publish a power rating. Aune S17 Pro EVO publishes at 32 Ω, at 150 Ω, at 300 Ω and at 600 Ω; Grace Design m900 at 32 Ω, at 300 Ω and at 600 Ω. The other rows are worked out from those.
So the two columns are not equally firm row by row: at 150 Ω only the Aune S17 Pro EVO figure is the maker’s own. On those rows the derived number is the one to doubt first.
On power they are interchangeable across this whole database: there is no headphone here that one reaches 100 dB on and the other does not.
15 headphones are left alone by the Grace Design m900 under the one-eighth rule but coloured by the Aune S17 Pro EVO (64 Audio Nio, 64 Audio Volur, Campfire Audio Andromeda 2023, 12 more).
567 of the 567 models here reach 100 dB on both.
Headroom is at a 100 dB SPL peak.
The widest gap on the list is the Audio-Technica ATH-R70X: Aune S17 Pro EVO has +20 dB of headroom there against +17 dB. 3 dB is about 2.1 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Aune S17 Pro EVO because that maker publishes no output noise figure.
| Headphone | Impedance | Needs | Aune S17 Pro EVO headroom | Grace Design m900 headroom | Aune S17 Pro EVO hiss | Grace Design m900 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +42 dB | +44 dB | not published | 28 dB |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +22 dB | +24 dB | not published | 8 dB |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +31 dB | +28 dB | not published | 7 dB |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +27 dB | +23 dB | not published | 2 dB |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +23 dB | +22 dB | not published | 1 dB |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +20 dB | +17 dB | not published | -5 dB |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +16 dB | +12 dB | not published | -9 dB |
| HiFiMAN Susvara | 60 Ω | 50 mW | +13 dB | +11 dB | not published | -11 dB |
The Aune S17 Pro EVO costs $139 more than the Grace Design m900, and on these three axes the money buys nothing: among the 567 models here there is not one that the Aune S17 Pro EVO handles and the Grace Design m900 does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper Grace Design m900 leaves 15 models alone under the one-eighth rule that the Aune S17 Pro EVO does not.
Only published figures count here; blank axes are counted separately.
Each in full: Aune S17 Pro EVO and Grace Design m900.