Siblings in PS Audio's Stellar range, so they share a design and a house sound. It comes down to power, features and price.
| Area | Better | Why |
|---|
| Power | B | PS Audio Stellar S300 has more power - 140W against 100W into 8 ohms. That is about 1.5dB, which is a small step in loudness but real headroom on peaks. |
| Room size | depends | We rate PS Audio Stellar Strata MK2 the better fit for a small room, and PS Audio Stellar S300 for 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 | B | PS Audio Stellar S300 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. |
| Built-in DAC | A | PS Audio Stellar Strata MK2 has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | evenly matched | The same number of line-level inputs (1). |
| Phono stage | depends | PS Audio Stellar Strata MK2 has a built-in phono stage and PS Audio Stellar S300 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. |
| Headphones | depends | Only PS Audio Stellar Strata MK2 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Price | B | PS Audio Stellar S300 costs less - $1,999 against $3,499 at list. |
| Watts per dollar | B | PS Audio Stellar S300 is the cheaper watt - about $14 per watt against $35. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A PS Audio Stellar Strata MK2 B PS Audio Stellar S300
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?
PS Audio Stellar S300 is the easier recommendation: it leads on most of the measured areas and costs less. Take PS Audio Stellar Strata MK2 if one of the "depends" rows above describes your system. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - PS Audio Stellar S300 is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. If you play records, PS Audio Stellar Strata MK2 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.