An amp doesn't have a damping factor. Damping factor is the ratio of the rated impedance of the loudspeaker to the source impedance.
The convention is to report Damping Factor into an 8 ohm load - so for pratical purposes one might say that power amps do indeed have a Damping Factor.
It can be over rated as the woofer drive motor and mechanical as well as acoustic suspension can play a much bigger role. A high damping factor amp is not going to fix a badly designed speaker with low cost drivers with cheap (small) motor - that will be putting lipstick on a pig.