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 | NAD Masters Series M33 has more power - 200W against 150W into 8 ohms. That is about 1.2dB, 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 nearly doubles (300W and 380W). |
| Noise floor | B | NAD Masters Series M33 is the quieter design on paper - 120dB against 100dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | A | Both decode on board. Primare I35 Prisma goes higher - 768kHz against 192kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | evenly matched | Only Primare I35 Prisma has Chromecast; only NAD Masters Series M33 has BluOS. Neither list is longer in a way that matters - check the one service you actually pay for. |
| Analogue inputs | A | Primare I35 Prisma takes more analogue sources - 5 against 2. |
| Phono stage | depends | NAD Masters Series M33 has a built-in phono stage (MM,MC) and Primare I35 Prisma 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. |
| Headphones | depends | Only NAD Masters Series M33 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Price | evenly matched | Priced within a few per cent of each other. |
| Watts per dollar | B | NAD Masters Series M33 is the cheaper watt - about $30 per watt against $39. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Primare I35 Prisma B NAD Masters Series M33
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?
NAD Masters Series M33 has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. If you play records, NAD Masters Series M33 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.