These are not the same size of amplifier: Rotel RA-1572 MKII has roughly 2x the power of Primare I15 Prisma. That is about 3dB, 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 | B | Rotel RA-1572 MKII has more power - 120W against 60W into 8 ohms. That is about 3dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate Primare I15 Prisma the better fit for desk or near-field listening and a small room, and Rotel RA-1572 MKII for a mid-size room, a large room and a very large room. Match the amplifier to the room you actually have, not the one you want. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output increases strongly (100W and 200W). |
| Noise floor | B | Rotel RA-1572 MKII is the quieter design on paper - 100dB against 97dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | A | Both decode on board. Primare I15 Prisma goes higher - 768kHz against 384kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | A | Only Primare I15 Prisma has AirPlay 2 and Chromecast. |
| Analogue inputs | B | Rotel RA-1572 MKII takes more analogue sources - 4 against 1. |
| Phono stage | depends | Rotel RA-1572 MKII has a built-in phono stage (MM) and Primare I15 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 Rotel RA-1572 MKII has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier class | depends | Primare I15 Prisma is Class D and Rotel RA-1572 MKII is Class A/B. Class D runs cool and draws almost nothing at idle; Class A/B runs warm and is the long-established mainstream choice. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | Primare I15 Prisma takes up about 17% less shelf area (1387cm² against 1675cm²). |
| Price | evenly matched | Priced within a few per cent of each other. |
| Watts per dollar | B | Rotel RA-1572 MKII is the cheaper watt - about $18 per watt against $37. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Primare I15 Prisma B Rotel RA-1572 MKII
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?
Rotel RA-1572 MKII has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. 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 - Rotel RA-1572 MKII 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 60 watts would be headroom you pay for and never hear - we rate Rotel RA-1572 MKII poorly for near-field use for exactly that reason. If you play records, Rotel RA-1572 MKII 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.