These are not the same size of amplifier: NAD C 700 has roughly 2x the power of NAD C 328. That is about 3dB, so it is a question of room size and how hard your speakers are to drive, not of one being the better amplifier.
| Area | Better | Why |
|---|
| Power | B | NAD C 700 has more power - 80W against 40W into 8 ohms. That is about 3dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate NAD C 328 the better fit for desk or near-field listening and a small room, and NAD C 700 for a mid-size room, a large room and 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 barely increases (40W and 80W). |
| Noise floor | A | NAD C 328 is the quieter design on paper - 100dB against 84dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Both decode on board, but only NAD C 700 handles MQA. |
| Streaming | B | Only NAD C 700 has AirPlay 2, Roon and BluOS. |
| Analogue inputs | evenly matched | The same number of line-level inputs (2). |
| Phono stage | depends | NAD C 328 has a built-in phono stage (MM) 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. |
| Room to grow | evenly matched | The same expansion options on both. |
| Headphones | depends | Only NAD C 328 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Shelf space | depends | NAD C 700 takes up about 52% less shelf area (651cm² against 1349cm²). |
| Price | A | NAD C 328 costs less - $699 against $1,599 at list. |
A NAD C 328 B NAD C 700
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: NAD C 700 measures better, NAD C 328 costs about 56% less. With most speakers in most rooms that gap is smaller in practice than it looks here. Start with the room. In a large or open-plan room, or with speakers that are hard to drive - low sensitivity, or an impedance that dips - NAD C 700 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 40 watts is already more than most people ever use, and the extra 40 watts would be headroom you pay for and never hear - we rate NAD C 700 poorly for near-field use for exactly that reason. If you play records, NAD C 328 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.