One is a streaming all-in-one and the other is an amplifier. Judge them on how many boxes you want and what you already own, not on the spec sheet alone.
| Area | Better | Why |
|---|
| Power | B | NAD C 368 BluOS-2i has more power - 80W against 60W 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 NAD D 3045 the better fit for desk or near-field listening and a small room, and NAD C 368 BluOS-2i 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. |
| Noise floor | evenly matched | Much the same signal-to-noise ratio (98dB vs 98dB). |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Streaming | B | Only NAD C 368 BluOS-2i has AirPlay 2, Roon and BluOS. |
| Analogue inputs | evenly matched | The same number of line-level inputs (2). |
| Room to grow | evenly matched | The same expansion options on both. |
| Shelf space | depends | NAD D 3045 takes up about 89% less shelf area (208cm² against 1840cm²), and it is 134mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | NAD D 3045 costs less - $899 against $1,749 at list. |
| Watts per dollar | A | NAD D 3045 is the cheaper watt - about $15 per watt against $22. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A NAD D 3045 B NAD C 368 BluOS-2i
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?
NAD C 368 BluOS-2i is ahead, but on only 1 of the measured areas, and it costs about 95% more. That is a lot of money for a narrow margin - NAD D 3045 is the sensible buy unless a specific feature above decides it for you. Think about the whole system: the roughly $850 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.