I agree with Stan -- if you are happy with the sound leave it as is. Absolute phase reversal on the main speakers will be inaudible on most recordings, and on the few recordings on which it may make a difference, the difference will be minor.
However, what COULD do damage would be reversing the hot and ground input leads within the sub. You didn't fully describe the setup, but if the sub has its own amplifier, and it is connected to the Cambridge's speaker output terminals, and both the sub and the Cambridge have 3-prong power cords, then depending on the design of the sub a reversal of its hot and ground inputs could result in shorting the Cambridge's hot output to ground, which would definitely not be healthy. And likewise if you are connecting line-level outputs of the Cambridge to the sub.
Regards,
-- Al
However, what COULD do damage would be reversing the hot and ground input leads within the sub. You didn't fully describe the setup, but if the sub has its own amplifier, and it is connected to the Cambridge's speaker output terminals, and both the sub and the Cambridge have 3-prong power cords, then depending on the design of the sub a reversal of its hot and ground inputs could result in shorting the Cambridge's hot output to ground, which would definitely not be healthy. And likewise if you are connecting line-level outputs of the Cambridge to the sub.
Regards,
-- Al