A valve amplifier against a solid-state one. They are not really rivals: they differ in character, in what they will drive and in what owning them involves, so start there rather than with the watts.
| Area | Better | Why |
|---|
| Power | B | Onkyo Muse Y-50 has more power - 125W against 100W into 8 ohms. That is about 1dB, which is a small step in loudness but real headroom on peaks. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output nearly doubles (200W and 250W). |
| Built-in DAC | B | Onkyo Muse Y-50 has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Use with a TV | depends | Only Onkyo Muse Y-50 has HDMI, so the television can drive it directly and one remote controls the volume. If the system is for music only, this changes nothing. |
| Amplifier type | depends | Rogue Audio Sphinx v3 is Hybrid and Onkyo Muse Y-50 is Solid State. Valve designs are usually warmer and softer at the limits and need their tubes replaced eventually; solid state is the lower-maintenance choice. This is a taste and ownership decision, not a quality one. |
| Price | B | Onkyo Muse Y-50 costs less - $1,500 against $1,795 at list. |
| Watts per dollar | B | Onkyo Muse Y-50 is the cheaper watt - about $12 per watt against $18. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Rogue Audio Sphinx v3 B Onkyo Muse Y-50
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?
Onkyo Muse Y-50 is the easier recommendation: it leads on most of the measured areas and costs less. Take Rogue Audio Sphinx v3 if one of the "depends" rows above describes your system. If this sits under a television, Onkyo Muse Y-50 is the one to buy - HDMI ARC means the TV remote controls the volume and there is no second box in the way. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Rogue Audio Sphinx v3 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.