Short answer
Both are desktop amplifiers, $660 against $699.
On raw power they are level: each reaches 100 dB on 567 of the 567 non-electrostatic models here.
| Specification | Grace Design m900 | Singxer SA-1 |
|---|---|---|
| Power into 32Ω | 1.0 W | 5.5 W |
| Power into 150Ω | 228 mW | 1.6 W |
| Power into 300Ω | 115 mW | 785 mW |
| Power into 600Ω | 57 mW | 380 mW |
| Output impedance | 0.08 Ω | 1.4 Ω |
| Output noise | 5.01 µV | 0.3 µV |
| Price | $660 | $699 |
| Headphones it reaches 100 dB on out of 567 | 567 | 567 |
| Load | Grace Design m900 | Singxer SA-1 |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Derived |
| 600 Ω | Published | Published |
Both makers publish a power rating. Grace Design m900 publishes at 32 Ω, at 300 Ω and at 600 Ω; Singxer SA-1 at 32 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 300 Ω only the Grace Design m900 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.
51 headphones are left alone by the Grace Design m900 under the one-eighth rule but coloured by the Singxer SA-1 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Nio, 48 more).
61 headphones stay below the audible-hiss threshold on the Singxer SA-1 but cross it on the Grace Design m900 (64 Audio Fourte, 64 Audio Nio, 64 Audio U12t, 58 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 Beyerdynamic DT 1990 Pro (250Ω): Singxer SA-1 has +32 dB of headroom there against +23 dB. 8 dB is about 6.9 times the power, which matters for peaks rather than for how loud the music sits.
Hiss below about 20 dB SPL is inaudible in a quiet room.
| Headphone | Impedance | Needs | Grace Design m900 headroom | Singxer SA-1 headroom | Grace Design m900 hiss | Singxer SA-1 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +44 dB | +52 dB damping | 28 dB | 4 dB |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +24 dB | +32 dB damping | 8 dB | -16 dB |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +28 dB | +36 dB | 7 dB | -18 dB |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +23 dB | +32 dB | 2 dB | -22 dB |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +22 dB | +29 dB | 1 dB | -23 dB |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +17 dB | +25 dB | -5 dB | -29 dB |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +12 dB | +21 dB | -9 dB | -33 dB |
| HiFiMAN Susvara | 60 Ω | 50 mW | +11 dB | +18 dB | -11 dB | -35 dB |
The Singxer SA-1 costs $39 more than the Grace Design m900. Out of the 567 models here, that difference buys 61 more models kept below the audible-hiss threshold.
It does not run one way only: the cheaper Grace Design m900 leaves 51 models alone under the one-eighth rule that the Singxer SA-1 does not, which is the part worth checking against your own headphones before paying the difference.
Only published figures count here; blank axes are counted separately.
Each in full: Grace Design m900 and Singxer SA-1.