These are not the same size of amplifier: HiFi Rose RS520 has roughly 2.5x the power of Primare I25 Prisma. 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 | HiFi Rose RS520 has more power - 250W against 100W 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 HiFi Rose RS520 the better fit for a very large room, and Primare I25 Prisma 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 | B | Primare I25 Prisma holds up better into a 4-ohm load: its output nearly doubles to 200W, where the other barely increases. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | A | HiFi Rose RS520 is the quieter design on paper - 109dB against 100dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | A | Both decode on board, but only HiFi Rose RS520 handles MQA. |
| Streaming | B | Only Primare I25 Prisma has AirPlay 2 and Chromecast. |
| Analogue inputs | B | Primare I25 Prisma takes more analogue sources - 5 against 1. |
| Room to grow | evenly matched | The same expansion options on both. |
| Amplifier class | depends | HiFi Rose RS520 is Class AD and Primare I25 Prisma is Class D. 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 | HiFi Rose RS520 takes up about 42% less shelf area (1135cm² against 1970cm²), and it is 128mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | HiFi Rose RS520 costs less - $3,695 against $4,495 at list. |
| Watts per dollar | A | HiFi Rose RS520 is the cheaper watt - about $15 per watt against $45. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A HiFi Rose RS520 B Primare I25 Prisma
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?
HiFi Rose RS520 has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Primare I25 Prisma 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 - HiFi Rose RS520 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 100 watts is already more than most people ever use, and the extra 150 watts would be headroom you pay for and never hear - we rate HiFi Rose RS520 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.