it does not double the power when halving the impedance - but it is apparently stable at 2 ohm
No it’s "not bad" for a class-D, nowhere near doubling still, at least it goes up as the impedance goes down, too many either don’t go up at all at 2ohms or go backwards. "Could" be ok for the OP’s speakers if it's to be believed, and "may" get the best out of the low impedance bass they have.
600 Watts at 8 Ohms
800 Watts at 4 Ohms
1400 Watts at 2 Ohms
It will be interesting to see with independent tests if they give it to someone like Stereophile, if they have "underquoted the 8ohm and 4ohm" to make the 2ohm look as good as it is. As many manufacturers are doing that now, that you can see that on Stereophiles bench tests, it one way of making the amp look to be doubling, and it’s wrong (lying) and should be stamped out.
Sorry - the specs above are for stereo single amp - the power is considerably more in mono block configuration
If these are bridged stereo’s into mono’s? (probably as they give no specs) if so they won’t even do as good as the stereo amp in doubling down.
Cheers George