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 | Audio Research S-200 has more power - 200W against 150W into 8 ohms. That is about 1.2dB, which is a small step in loudness but real headroom on peaks. |
| Room size | depends | We rate Accuphase P-4600 the better fit for desk or near-field listening, a small room and a mid-size room, and Audio Research S-200 for 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 (300W and 400W). |
| Bass control | A | Accuphase P-4600 has the higher damping factor (800 vs 300), 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. |
| Analogue inputs | evenly matched | The same number of line-level inputs (2). |
| Price | B | Audio Research S-200 costs less - $12,950 against $13,975 at list. |
| Watts per dollar | B | Audio Research S-200 is the cheaper watt - about $65 per watt against $93. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Accuphase P-4600 B Audio Research S-200
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?
Audio Research S-200 has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is.
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.