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 | B | Marantz Model 30 has more power - 100W against 70W 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 Technics SU-G700M2 Grand Class the better fit for a small room, and Marantz Model 30 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 | evenly matched | Both behave much the same into 4 ohms - output nearly doubles (140W and 200W). |
| Built-in DAC | A | Technics SU-G700M2 Grand Class 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 2. |
| Room to grow | evenly matched | The same expansion options on both. |
| Price | A | Technics SU-G700M2 Grand Class costs less - $2,700 against $2,999 at list. |
| Watts per dollar | B | Marantz Model 30 is the cheaper watt - about $30 per watt against $39. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Technics SU-G700M2 Grand Class 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?
The usual trade-off: Marantz Model 30 measures better, Technics SU-G700M2 Grand Class costs about 10% less. With most speakers in most rooms that gap is smaller in practice than it looks here. 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.