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 | A | Buchardt I150 has more power - 150W against 100W into 8 ohms. That is about 1.8dB, which is a small step in loudness but real headroom on peaks. |
| Room size | depends | We rate Buchardt I150 the better fit for a very large room, and Marantz Model 30 for desk or near-field listening, a small room and a mid-size room. Match the amplifier to the room you actually have, not the one you want. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output nearly doubles (300W and 200W). |
| Bass control | A | Buchardt I150 has the higher damping factor (4500 vs 500), which usually means a tighter grip on a woofer. Above about 100 the returns flatten out, so read this as a tendency rather than a ranking. |
| Noise floor | A | Buchardt I150 is the quieter design on paper - 121dB against 88dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | A | Buchardt I150 has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | B | Marantz Model 30 takes more analogue sources - 6 against 1. |
| Phono stage | depends | Marantz Model 30 has a built-in phono stage (MM,MC) and Buchardt I150 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. |
| Headphones | depends | Only Marantz Model 30 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Shelf space | depends | Buchardt I150 takes up about 44% less shelf area (1147cm² against 2033cm²), and it is 149mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | Buchardt I150 costs less - $2,500 against $2,999 at list. |
| Watts per dollar | A | Buchardt I150 is the cheaper watt - about $17 per watt against $30. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Buchardt I150 B Marantz Model 30
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?
Buchardt I150 is the easier recommendation: it leads on most of the measured areas and costs less. Take Marantz Model 30 if one of the "depends" rows above describes your system. If you play records, Marantz Model 30 saves you buying a phono stage; if you do not, ignore that row entirely. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Marantz Model 30 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.