I read that D.F. factor is the ratio {speackers real impedace/[amps output impedance+wire impedance]} .
Here is the link about DF(maybe all in this member already knew?)
http://www.crownaudio.com/pdf/amps/damping%20factor.pdf
I think DF have a some value for a fine sounds and can't say meaningless.
Maybe,It's difficult to design low output impedance circuit.
If Power means voltage*current,there needs more & more capbility to providing enough current when driving 15 inch woofers.
It's my experience.
At least, To driving 4343B with tight & powerfull sound I needed MA2402, not MA1202 in spite of which can provide 285W+285W power!
There was a obious difference bitween 2402 to 1202.
One is embiant sounds. 2402 can express enough surrownding atmosphear.
Two is clear mid sounds. especialliy for male vocal.
Three is base sounds. only the enough power can drive Hip base sounds. it may be over 500W+500W! so it needs MA2402.
When I used accuphase M-100 mono power amps, Power was enouph but it had a little caractor.
Thats why I changed to Crown PA amps .
Anyway, in my opinion, There needs over 500W+500W & DF1000 for diving 4343B with hi-fi sounds , I feel.
but I know power & DF is only one side elements of measurement.