One is a streaming all-in-one and the other is an amplifier. Judge them on how many boxes you want and what you already own, not on the spec sheet alone.
| Area | Better | Why |
|---|
| Power | B | Anthem STR 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 400W). |
| Noise floor | B | Anthem STR 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 | A | Only Primare I35 Prisma has AirPlay 2, Chromecast and Roon. |
| Analogue inputs | evenly matched | The same number of line-level inputs (5). |
| Phono stage | depends | Anthem STR 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. |
| Amplifier class | depends | Primare I35 Prisma is Class D and Anthem STR 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. |
| Price | B | Anthem STR costs less - $5,000 against $5,795 at list. |
| Watts per dollar | B | Anthem STR is the cheaper watt - about $25 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 Anthem STR
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?
Anthem STR 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, Anthem STR 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.