It is not important at all. It is just another way of expressing the amplifier’s output impedance.
Most SS amps have an output impedance of 0.04 ohms, which is a DF of 200 or 8 divided by 0.04. If you include speaker cable impedance of, say, 0.1 ohm that means the speaker is at 98.3% of the amplifier load and the amplifier’s output impedance is 0.5% of the load, an almost perfect voltage source that is immune from the speaker’s varying load.
If you substitute an amp with a 2000 DF, it has an output impedance of 0.004 ohms and that is 0.05% of the total load. That is only a change of 0.45% with respect to the amplifier’s contribution. The speaker is 98.7% of the load, despite the amplifier being a more perfect voltage source by a factor of 10.
I seriously doubt that 0.45% change is audible. However, a general rule of thumb is that an amp with a DF of 20 or below has sonic consequences. Doing the math, the speaker in this case is 95% of the load -- a considerable change that results in sonic degradation from dynamic load variation since the amplifer is no longer a perfect voltage source .
Almost all of today’s SS amps use global NFB and high quality output transistors. It is the norm to see output impedances ranging from 0.01 to 0.05 ohms. That’s why you don’t have to worry about it.
