I didn't mean disrespect to the M6, but as I've owned $450 IEMs in the past and own several thousand dollars in audio equipment, you may easier understand how $20 IEMs like the M6 are more of a throw-away pair for me! For the price, they are absolutely excellent, some of my favorite budget IEMs out there.
For the M2, yeah I've had them and just bought a couple of them. For $6, you can't go wrong. Pretty solid build quality for the price.
These vs. the N9 how do they compare