A valve amplifier against a solid-state one. They are not really rivals: they differ in character, in what they will drive and in what owning them involves, so start there rather than with the watts.
| Area | Better | Why |
|---|
| Power | A | PS Audio BHK Mono 300 has more power - 300W against 200W into 8 ohms. That is about 1.8dB, 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 (600W and 400W). |
| Analogue inputs | evenly matched | The same number of line-level inputs (1). |
| Amplifier type | depends | PS Audio BHK Mono 300 is Hybrid and PS Audio PMG M400 is Solid State. Valve designs are usually warmer and softer at the limits and need their tubes replaced eventually; solid state is the lower-maintenance choice. This is a taste and ownership decision, not a quality one. |
| Shelf space | depends | PS Audio BHK Mono 300 takes up about 15% less shelf area (1544cm² against 1806cm²), and it is 51mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | PS Audio BHK Mono 300 costs less - $8,499 against $8,999 at list. |
| Watts per dollar | A | PS Audio BHK Mono 300 is the cheaper watt - about $28 per watt against $45. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A PS Audio BHK Mono 300 B PS Audio PMG M400
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 BHK Mono 300 has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is.
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.