No single best amplifier here. What decides it is what you have to drive, what you need to plug in, and how much of the system you want in one box.
| Area | Better | Why |
|---|
| Power | A | OSD Nero Stream XD2 has more power - 60W against 45W into 8 ohms. That is about 1.2dB, which is a small step in loudness but real headroom on peaks. |
| Noise floor | B | Denon PMA-600NE is the quieter design on paper - 105dB against 95dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Analogue inputs | B | Denon PMA-600NE takes more analogue sources - 4 against 1. |
| Phono stage | depends | Denon PMA-600NE 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 | OSD Nero Stream XD2 is Class D and Denon PMA-600NE is Class A/B. Class D runs cool and draws almost nothing at idle; Class A/B runs warm and is the long-established mainstream choice. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | OSD Nero Stream XD2 takes up about 51% less shelf area (688cm² against 1405cm²), and it is 42mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | OSD Nero Stream XD2 costs less - $400 against $499 at list. |
| Watts per dollar | A | OSD Nero Stream XD2 is the cheaper watt - about $7 per watt against $11. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A OSD Nero Stream XD2 B Denon PMA-600NE
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?
Neither runs away with it - they trade advantages. Let the "depends" rows and the speakers you already own settle it. If you play records, Denon PMA-600NE 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.