I went through my house with a video camera a while back and recorded all of my electronics, recorded the serial numbers, and took photos of receipts if I had them. I placed it all on a cd in case I was robbed or something.
In your case, you have all of the equipment sitting in your house (broken, but still there) so I guess that would be proof enough that you own the item and that it is broken due to lightning strike.
Hopefully they don't estimated the depreciated value of your equipment well below what it is worth (I don't think they will give you what you paid for everything)
good luck!
