A generation apart: Q Acoustics M20 HD is the newer design, against a 2016 model. Newer is not automatically better, but the older one is more likely to be discounted or near run-out.
| Area | Better | Why |
|---|
| Bass | B | Audioengine HD6 digs deeper - 50Hz against 55Hz. A subwoofer would even that out. |
| Built-in power | A | Q Acoustics M20 HD has the bigger amplifier (128W vs 100W RMS). |
| Connections | A | Q Acoustics M20 HD adds streaming. |
| Size | depends | Similar cabinet size - neither is easier to fit. |
| Expandability | depends | Q Acoustics M20 HD: a sub output; Audioengine HD6: a sub output. |
| Price | A | Q Acoustics M20 HD is cheaper - $599 against $699, about 14% less. |
A Q Acoustics M20 HD B Audioengine HD6
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 speakers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
Q Acoustics M20 HD has the edge on paper, though the margin is not large. The rows marked "depends" may matter more to you than the score does. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 55Hz anyway, which makes the cheaper Q Acoustics M20 HD much easier to justify.
And remember what a spec sheet cannot show: how each looks in your room and whether the finish suits it, what dealer support and warranty are like where you live, and how they actually sound to you. If you can hear them first - ideally with your own music - that will tell you more than any number above.