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 | McIntosh MSA5500 has more power - 100W against 80W into 8 ohms. That is about 1dB, which is a small step in loudness but real headroom on peaks. |
| Built-in DAC | B | Both decode on board, but only Naim Uniti Nova handles DSD. |
| Streaming | evenly matched | The same streaming platforms and services on both. |
| Phono stage | depends | McIntosh MSA5500 has a built-in phono stage and Naim Uniti Nova 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 | A | Only McIntosh MSA5500 offers a pre-out/main-in loop - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Shelf space | depends | Naim Uniti Nova takes up about 45% less shelf area (1371cm² against 2512cm²), and it is 249mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Naim Uniti Nova costs less - $6,899 against $8,000 at list. |
A McIntosh MSA5500 B Naim Uniti Nova
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: McIntosh MSA5500 measures better, Naim Uniti Nova costs about 14% less. With most speakers in most rooms that gap is smaller in practice than it looks here. If you play records, McIntosh MSA5500 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.