Where can I buy Extrema's woofer in Italy or USA?

Hi, there!

This is Choi in Korea
Unfortunately, I blew the woofer of my speaker , Sonus Faber Extrema, few days ago.
One woofer is damaged, so I need to replace it.
I wonder if where I can buy a matched pair of Extrema's woofer.
I'd like to buy a pair of woofer with Sonus Faber Logo on them.

And also I need to find out the reason why my speakers were damaged because I'll continue to use my current system.
Do you have any idea as to why my woofer blew up? If you know, would you please let me know?

My system is :

Power Amp: Plinius 250 Mk4
Pre-amp : Levinson 380S
Cd Player : Meridian 588
Speaker : Sonus Faber Extrema
(And I use Automatic Voltage Regulator to maintain clean electric power)

Thanks!