Surround speakers for Martin Logan CLS

I am planning on adding additional surround speakers to my Martin Logan CLS stereo pair of speakers.
Although I know that the best way should be to go with ML surrounds, I am considering to go with 7.1 setup and this would require additional wall mounted surrounds.
Do you have any suggestions for surrounds (preferably dipoles) that would match the timber of ML CLS. Another requirement is reproducible low frequency of these surrounds to be 45-50 Hz.
Thank you in advance for your input.