These are not the same size of amplifier: PS Audio Stellar M1200 has roughly 2x the power of PS Audio BHK Mono 300. 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 | A | PS Audio Stellar M1200 has more power - 600W against 300W into 8 ohms. That is about 3dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output nearly doubles (1200W and 600W). |
| Noise floor | A | PS Audio Stellar M1200 is the quieter design on paper - 112dB against 85dB. Audible mainly with sensitive speakers in a quiet room. |
| Analogue inputs | evenly matched | The same number of line-level inputs (1). |
| Amplifier class | depends | PS Audio Stellar M1200 is Class D and PS Audio BHK Mono 300 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 | PS Audio Stellar M1200 takes up about 15% less shelf area (1316cm² against 1544cm²), and it is 51mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | PS Audio Stellar M1200 costs less - $3,499 against $8,499 at list. |
| Watts per dollar | A | PS Audio Stellar M1200 is the cheaper watt - about $6 per watt against $28. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A PS Audio Stellar M1200 B PS Audio BHK Mono 300
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 M1200 is the easier recommendation: it leads on most of the measured areas and costs less. Take PS Audio BHK Mono 300 if one of the "depends" rows above describes your system. 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 - PS Audio Stellar M1200 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 300 watts is already more than most people ever use, and the extra 300 watts would be headroom you pay for and never hear - we rate PS Audio Stellar M1200 poorly for near-field use for exactly that reason. Think about the whole system: the roughly $5,000 saved by taking the cheaper one would buy better speakers or a subwoofer, which does more for the sound than the difference between two competent amplifiers.
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.