These are not the same size of amplifier: Primare I35 has roughly 2.5x the power of Primare I15. That is about 4dB, 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 | A | Primare I35 has more power - 150W against 60W into 8 ohms. That is about 4dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate Primare I35 the better fit for a large room and a very large room, and Primare I15 for desk or near-field listening, a small room and a mid-size room. Match the amplifier to the room you actually have, not the one you want. |
| Grip on hard loads | A | Primare I35 holds up better into a 4-ohm load: its output nearly doubles to 300W, where the other increases strongly. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | A | Primare I35 is the quieter design on paper - 100dB against 97dB. Audible mainly with sensitive speakers in a quiet room. |
| Analogue inputs | evenly matched | The same number of line-level inputs (5). |
| Room to grow | evenly matched | The same expansion options on both. |
| Shelf space | depends | Primare I15 takes up about 30% less shelf area (1387cm² against 1970cm²), and it is 63mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Primare I15 costs less - $1,695 against $4,595 at list. |
A Primare I35 B Primare I15
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: Primare I35 measures better, Primare I15 costs about 63% less. With most speakers in most rooms that gap is smaller in practice than it looks here. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Primare I35 is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. 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 - Primare I35 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 60 watts is already more than most people ever use, and the extra 90 watts would be headroom you pay for and never hear - we rate Primare I35 poorly for near-field use for exactly that reason.
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.