These are not the same size of amplifier: OSD Nero Stream XD2 has roughly 2x the power of Onkyo A-9110. That is about 3dB, so it is a question of room size and how hard your speakers are to drive, not of one being the better amplifier.
| Area | Better | Why |
|---|
| Power | B | OSD Nero Stream XD2 has more power - 60W against 30W into 8 ohms. That is about 3dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Noise floor | A | Onkyo A-9110 is the quieter design on paper - 103dB against 95dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | OSD Nero Stream XD2 has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Phono stage | depends | Onkyo A-9110 has a built-in phono stage (MM) and OSD Nero Stream XD2 does not. Decisive if you own a turntable, completely irrelevant if you do not - and an outboard phono stage is easy to add later either way. |
| Room to grow | evenly matched | The same expansion options on both. |
| Amplifier class | depends | Onkyo A-9110 is Class A/B and OSD Nero Stream XD2 is Class D. Class A/B runs warm and is the long-established mainstream choice; Class D runs cool and draws almost nothing at idle. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | OSD Nero Stream XD2 takes up about 52% less shelf area (688cm² against 1434cm²), and it is 49mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | Onkyo A-9110 costs less - $349 against $400 at list. |
| Watts per dollar | B | OSD Nero Stream XD2 is the cheaper watt - about $7 per watt against $12. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Onkyo A-9110 B OSD Nero Stream XD2
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?
The usual trade-off: OSD Nero Stream XD2 measures better, Onkyo A-9110 costs about 13% less. With most speakers in most rooms that gap is smaller in practice than it looks here. Start with the room. In a large or open-plan room, or with speakers that are hard to drive - low sensitivity, or an impedance that dips - OSD Nero Stream XD2 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 30 watts is already more than most people ever use, and the extra 30 watts would be headroom you pay for and never hear. If you play records, Onkyo A-9110 saves you buying a phono stage; if you do not, ignore that row entirely.
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.