Short answer
Both are audio interfaces, $249 against $299.
The SSL 2 Plus MkII reaches 100 dB on 565 of the 567 models here, the Audient EVO 8 on 543.
| Specification | Audient EVO 8 | SSL 2 Plus MkII |
|---|---|---|
| Power into 32Ω | 22 mW | 374 mW |
| Power into 150Ω | 14 mW | 80 mW |
| Power into 300Ω | 11 mW | 40 mW |
| Power into 600Ω | 10 mW | 20 mW |
| Output impedance | 50 Ω | 1 Ω |
| Output noise | not published | not published |
| Price | $249 | $299 |
| Headphones it reaches 100 dB on out of 567 | 543 | 565 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | Audient EVO 8 | SSL 2 Plus MkII |
|---|---|---|
| 32 Ω | Derived | Upper bound |
| 150 Ω | Derived | Upper bound |
| 300 Ω | Derived | Upper bound |
| 600 Ω | Recomputed | Upper bound |
Neither column is a power rating, and the two are not even weak in the same way. The SSL 2 Plus MkII figures are ceilings worked out from a maximum output voltage, on the assumption that the amplifier holds it into the load. The Audient EVO 8 figures are worked out from figures its maker did publish — power at other loads, or the voltage printed beside it. The second method understates; the first flatters. That is the wrong way round for reading the table straight across, so a gap in favour of the SSL 2 Plus MkII is the one to doubt.
22 headphones reach 100 dB on the SSL 2 Plus MkII but not on the Audient EVO 8 — Dan Clark Audio AEON 2 Closed, Dan Clark Audio AEON 2 Noire, Dan Clark Audio AEON 2 Open, 19 more.
546 headphones are left alone by the SSL 2 Plus MkII under the one-eighth rule but coloured by the Audient EVO 8 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Ocean, 543 more).
543 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 HiFiMAN HE400se: SSL 2 Plus MkII has +16 dB of headroom there against +4 dB. 12 dB is about 16 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Audient EVO 8 and SSL 2 Plus MkII because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Audient EVO 8 headroom | SSL 2 Plus MkII headroom | Audient EVO 8 hiss | SSL 2 Plus MkII hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +22 dB damping | +34 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +2 dB damping | +14 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +15 dB damping | +23 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +13 dB damping | +19 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +4 dB damping | +16 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +8 dB | +12 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +2 dB damping | +8 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | -3 dB damping | +6 dB | not published | not published |
The SSL 2 Plus MkII costs $50 more than the Audient EVO 8. Out of the 567 models here, that difference buys 22 more models driven to 100 dB and 546 more models left alone under the one-eighth rule.
Nothing runs the other way: there is no axis here on which the cheaper of the two does better.
Only published figures count here; blank axes are counted separately.
Each in full: Audient EVO 8 and SSL 2 Plus MkII.