and like you whether the doubling of output impedance would pose a problem in regards to the very low impedance the CLX has above 8 kilohertz.Yes and this is why you should get the "correct amp" that has no problem with this loading. And not gamble that bridged AHB2 are going to remain stable and handle the 1ohm loading.
As for tubes with this loading it is also why all the ones I have heard into my ML's have sounded "distant/muted" in the top end, lacking sparkle and air.
Cheers George