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 | Rogue Audio Sphinx v3 has more power - 100W against 80W into 8 ohms. That is about 1dB, which is a small step in loudness but real headroom on peaks. |
| Grip on hard loads | B | Rogue Audio Sphinx v3 holds up better into a 4-ohm load: its output nearly doubles to 200W, where the other barely increases. That matters with demanding speakers far more than the 8-ohm figure does. |
| Built-in DAC | A | NAD C 700 has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | B | Rogue Audio Sphinx v3 takes more analogue sources - 4 against 2. |
| Phono stage | depends | Rogue Audio Sphinx v3 has a built-in phono stage (MM and MC, 44 dB and 60 dB gain) and NAD C 700 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. |
| Use with a TV | depends | Only NAD C 700 has HDMI eARC, so the television can drive it directly and one remote controls the volume. If the system is for music only, this changes nothing. |
| Headphones | depends | Only Rogue Audio Sphinx v3 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier type | depends | NAD C 700 is Solid State and Rogue Audio Sphinx v3 is Hybrid. 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 | A | NAD C 700 costs less - $1,599 against $1,795 at list. |
A NAD C 700 B Rogue Audio Sphinx v3
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?
The usual trade-off: Rogue Audio Sphinx v3 measures better, NAD C 700 costs about 11% less. With most speakers in most rooms that gap is smaller in practice than it looks here. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Rogue Audio Sphinx v3 is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. If you play records, Rogue Audio Sphinx v3 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.