Different price classes - OSD Nero Stream XD costs roughly 1.6x what Fosi Audio ZA3 does. Expect it to lead on paper; the question is whether you will hear the difference through the speakers you own.
| Area | Better | Why |
|---|
| Speaker load rating | A | Fosi Audio ZA3 is rated down to 2 ohms against 4, so it is the safer partner for a low-impedance speaker. |
| Noise floor | A | Fosi Audio ZA3 is the quieter design on paper - 106dB against 95dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | OSD Nero Stream XD has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | A | Fosi Audio ZA3 takes more analogue sources - 2 against 1. |
| Room to grow | evenly matched | The same expansion options on both. |
| Headphones | depends | Only OSD Nero Stream XD has a headphone output. Worth something if you listen late, nothing if you never do. |
| Shelf space | depends | Fosi Audio ZA3 takes up about 26% less shelf area (285cm² against 384cm²). |
| Price | A | Fosi Audio ZA3 costs less - $150 against $240 at list. |
A Fosi Audio ZA3 B OSD Nero Stream XD
depends neither is better in the abstract - it turns on your room, your system or how you will use them. Only specs published for both amplifiers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
Fosi Audio ZA3 is the easier recommendation: it leads on most of the measured areas and costs less. Take OSD Nero Stream XD if one of the "depends" rows above describes your system. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Fosi Audio ZA3 becomes the more rational buy. Think about the whole system: the roughly $90 saved by taking the cheaper one would buy better speakers or a subwoofer, which does more for the sound than the difference between two competent amplifiers.
What a spec sheet cannot show: how either sounds with your speakers, how the controls feel day to day, and what the app is like to live with - which is where most all-in-one amplifiers are actually won or lost. Power figures are the manufacturers' own and are not measured to a common standard, so treat small differences as noise. If you can hear both, that will tell you more than any row above.