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 | A | Arcam SA45 has more power - 180W against 125W into 8 ohms. That is about 1.6dB, which is a small step in loudness but real headroom on peaks. |
| Grip on hard loads | B | Mark Levinson No.5802 holds up better into a 4-ohm load: its output nearly doubles to 250W, where the other increases strongly. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | A | Arcam SA45 is the quieter design on paper - 110dB against 103dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Both decode on board, but only Mark Levinson No.5802 handles DSD and MQA. |
| Streaming | A | Only Arcam SA45 has AirPlay 2, Chromecast and Roon. |
| Phono stage | depends | Arcam SA45 has a built-in phono stage and Mark Levinson No.5802 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 Mark Levinson No.5802 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier class | depends | Arcam SA45 is Class G and Mark Levinson No.5802 is Class A/B. Class G/H switches its supply rails to cut the heat a Class A/B design wastes; 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 | Arcam SA45 takes up about 27% less shelf area (1796cm² against 2454cm²), and it is 145mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | Arcam SA45 costs less - $5,500 against $8,500 at list. |
| Watts per dollar | A | Arcam SA45 is the cheaper watt - about $31 per watt against $68. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Arcam SA45 B Mark Levinson No.5802
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?
Arcam SA45 is the easier recommendation: it leads on most of the measured areas and costs less. Take Mark Levinson No.5802 if one of the "depends" rows above describes your system. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Mark Levinson No.5802 is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. If you play records, Arcam SA45 saves you buying a phono stage; if you do not, ignore that row entirely.
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.