I can't see any measurements on the CM8 regarding impedance as their nominal 8 ohm rating means nothing. It's the minimum impedance and at what frequency this happens that determines whether an amplifier will likely drive a loudspeaker properly.
If your Cyrus amp is rated for 4 ohm loads, then I would expect it to drive the CM8 properly even if the impedance drops as I expect it would. If the amp is only rated at 8 ohms, then you'll need to find out what the CM8's minimum impedance is, and at what frequency.
Sorry I can't be more precise, but in the absence of detailed impedance information, it would just be speculation, which I try not to do.
EDIT - I've just read the spec on the Smartpower amp, and it is rated at 4 ohms, so would expect it to drive the CM8. It is also rated into 4 ohms in mono, so would expect it to do OK, but remember what I previously wrote about overheating in mono mode.