No single best amplifier here. What decides it is what you have to drive, what you need to plug in, and how much of the system you want in one box.
| Area | Better | Why |
|---|
| Power | evenly matched | Effectively the same output - 90W against 100W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Grip on hard loads | A | Yamaha A-S2200 holds up better into a 4-ohm load: its output increases strongly to 150W, where the other increases strongly. That matters with demanding speakers far more than the 8-ohm figure does. |
| Built-in DAC | B | 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 | A | Yamaha A-S2200 takes more analogue sources - 5 against 1. |
| Amplifier class | depends | Yamaha A-S2200 is Class A/B and PS Audio Stellar Strata MK2 is Class D. Class A/B runs warm and is the long-established mainstream choice; 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 | PS Audio Stellar Strata MK2 takes up about 30% less shelf area (1481cm² against 2127cm²), and it is 146mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | PS Audio Stellar Strata MK2 costs less - $3,499 against $4,500 at list. |
| Watts per dollar | B | PS Audio Stellar Strata MK2 is the cheaper watt - about $35 per watt against $50. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Yamaha A-S2200 B PS Audio Stellar Strata MK2
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?
Neither runs away with it - they trade advantages. Let the "depends" rows and the speakers you already own settle it. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Yamaha A-S2200 is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Yamaha A-S2200 becomes the more rational buy.
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.