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 | evenly matched | Effectively the same output - 72W against 70W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Built-in DAC | B | Denon PMA-1700NE has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | A | Rega Elex-R takes more analogue sources - 4 against 3. |
| Room to grow | A | Only Rega Elex-R offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Shelf space | depends | Rega Elex-R takes up about 29% less shelf area (1376cm² against 1949cm²), and it is 128mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | Rega Elex-R costs less - $1,395 against $2,099 at list. |
| Watts per dollar | A | Rega Elex-R is the cheaper watt - about $19 per watt against $30. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Rega Elex-R B Denon PMA-1700NE
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?
Rega Elex-R is the easier recommendation: it leads on most of the measured areas and costs less. Take Denon PMA-1700NE if one of the "depends" rows above describes your system. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Rega Elex-R becomes the more rational buy. Think about the whole system: the roughly $704 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.