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 | B | Naim Nova PE has more power - 150W against 100W into 8 ohms. That is about 1.8dB, which is a small step in loudness but real headroom on peaks. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output increases strongly (160W and 250W). |
| Built-in DAC | B | Both decode on board, but only Naim Nova PE 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 Nova PE 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. |
| Amplifier class | depends | McIntosh MSA5500 is Class A/B and Naim Nova PE 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 | Naim Nova PE takes up about 54% less shelf area (1145cm² against 2512cm²), and it is 300mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | McIntosh MSA5500 costs less - $8,000 against $9,999 at list. |
A McIntosh MSA5500 B Naim Nova PE
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: Naim Nova PE measures better, McIntosh MSA5500 costs about 20% 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.