One is a streaming all-in-one and the other is an amplifier. Judge them on how many boxes you want and what you already own, not on the spec sheet alone.
| Area | Better | Why |
|---|
| Power | B | JBL SA750 75th Anniversary Edition has more power - 130W against 100W into 8 ohms. That is about 1.1dB, which is a small step in loudness but real headroom on peaks. |
| Grip on hard loads | A | Marantz Model 30 holds up better into a 4-ohm load: its output nearly doubles to 200W, where the other increases strongly. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | B | JBL SA750 75th Anniversary Edition is the quieter design on paper - 112dB against 88dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | JBL SA750 75th Anniversary Edition has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Streaming | B | Only JBL SA750 75th Anniversary Edition has AirPlay 2, Chromecast and Roon. |
| Analogue inputs | A | Marantz Model 30 takes more analogue sources - 6 against 4. |
| Room to grow | evenly matched | The same expansion options on both. |
| Amplifier class | depends | Marantz Model 30 is Class D and JBL SA750 75th Anniversary Edition is Class G. Class D runs cool and draws almost nothing at idle; Class G/H switches its supply rails to cut the heat a Class A/B design wastes. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | JBL SA750 75th Anniversary Edition takes up about 15% less shelf area (1718cm² against 2033cm²), and it is 78mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | evenly matched | Priced within a few per cent of each other. |
| Watts per dollar | B | JBL SA750 75th Anniversary Edition is the cheaper watt - about $23 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 Marantz Model 30 B JBL SA750 75th Anniversary Edition
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?
JBL SA750 75th Anniversary Edition has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Marantz Model 30 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 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.