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 Cinema 50 Series 2 has more power - 110W against 85W into 8 ohms. That is about 1.1dB, which is a small step in loudness but real headroom on peaks. |
| Speaker load rating | B | Marantz Cinema 50 Series 2 is rated down to 4 ohms against 8, so it is the safer partner for a low-impedance speaker. |
| Analogue inputs | B | Marantz Cinema 50 Series 2 takes more analogue sources - 5 against 3. |
| Phono stage | depends | Marantz Cinema 50 Series 2 has a built-in phono stage and ARCAM AVA15 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 | B | Only Marantz Cinema 50 Series 2 offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Built-in sources | depends | Marantz Cinema 50 Series 2 has a radio tuner built in. That is one less box if you still play discs or listen to radio, and dead weight if you do not. |
| Amplifier class | depends | ARCAM AVA15 is D and Marantz Cinema 50 Series 2 is AB. Class D runs cool and draws almost nothing at idle; 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. |
| Price | B | Marantz Cinema 50 Series 2 costs less - $3,000 against $4,500 at list. |
| Watts per dollar | B | Marantz Cinema 50 Series 2 is the cheaper watt - about $27 per watt against $53. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A ARCAM AVA15 B Marantz Cinema 50 Series 2
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?
Marantz Cinema 50 Series 2 is the easier recommendation: it leads on most of the measured areas and costs less. Take ARCAM AVA15 if one of the "depends" rows above describes your system. If you play records, Marantz Cinema 50 Series 2 saves you buying a phono stage; if you do not, ignore that row entirely. Think about the whole system: the roughly $1,500 saved by taking the cheaper one would buy better speakers or a subwoofer, which does more for the sound than the difference between two competent amplifiers.
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.