Power ratings are factual, but used as marketing gibberish.
"1,000 watts music power" is marketing B.S. that sounds more impressive than "500 watts continuous".
These are maximum power ratings for the voice coil at 1,000 Hz, before the coil melts into goo.
Since you don't play at 1,000 Hz... this is just baloney.
Cone excursion is what limits the amount of practical power you can input to your cab.
This is where proper tuning comes into play.
Power handling ability in a vented box drops DRASTICALLY below the tuning frequency.
If you have a vented box tuned at 52 Hz, it will not handle very much input power at all for low E (41 Hz), or worse for low B (31 Hz). The cone will travel beyond its mechanical limits and destroy itself.
#1 - understand the lowest note you will play
#2 - understand how much power the cab will actually accept down to this note.
#3 - understand how much noise you need to make, add cabs accordingly.
I do not subscribe to the 4-ohm cabs when an 8-ohm is available.
If I need to add a 2nd cab, many amps won't run properly with a 2-ohm load.
You lose nothing with 8-ohm cabs over 4-ohm, because most amps put out far more power than the cab can accept.
The image below is the Eminence design for the Delta 12LFa.
This is most likely the one used for the Avatar SB126 I just bought.
My criteria is 41 Hz as the lowest note.
I can input a maximum of 79 watts at 41 Hz, before I exceed the cone travel.