what effect does fire/heat/soot on digital equiptment?

Its digital. Digital is binary. Either works perfectly (perfect sound forever!) or not at all. 

This is very bad hope your stuff is not toast.

Cross fingers, Fire up -sorry ,and hopefully enjoy.

Place  a claim while you can and get a new system.

Soot is essentially carbon and it is conductive. I doubt they are damaged, but having them opened and cleaned, compressed air (non oiled) is generally enough.

I had a fire about thirty years ago and my speakers were toast, but all my ARC equipment was black and brown and worked just fine after a good cleaning. I still have the EC-2 crossover, but traded everything else over the years.

All the best.

JD

Oh, I did replace all the Caps and most of the resisters about 5 years later.

JD

This is why people carry insurance.  Also a great way to get something better.  However, how much is a 20 year old system worth.  I would think a 20 year system would have also reached far beyond its life expectancy.  

If you have filed a claim with your insurance company, they have most likely assigned a cleaning company to clean your house (walls, ceilings & floors). If they have assigned a national franchise (Servpro, Servicemaster, etc), they will know an electronics cleaning firm that will evaluate your components and clean them if it is possible. The same thing goes for dry cleaning your clothing. There are specialized professionals who you will need to use in most aspects of your claim. Best of luck to you!