My #@%$ Cat Destroyed My ARC REF 5SE. Soliciting Suggestions.

Ii was not your cat!!!!!  Door was open to your house- a bird came in as well as a cat. Do the math-=-=

oh man, sorry to hear. This was always a worry of mine when I had  big Levinson amp on the floor that all my cats sought for warmth. My new integrated fortunately fits on shelf with only an inch of room on top so they can no longer access. Glad to see you are a good, considerate cat dad and did not take it out on the poor scared kitty.
if the new board includes warranty and testing once installed, I would do it.

Very sorry for your situation. I agree 100% with teo_audio. I've repaired amps, preamps, crossovers and other gear with printed circuit boards, built circuit boards, amps, preamps, and more. I've rebuilt traces, cleaned boards, repaired burned board sections, and more. I would be very hesitant to declare it irreparable without actually seeing the damage, though I would not pay $6k for the board.

Would you be OK with posting pics? You can PM me with them if you wish. I won't do the work, but could possibly offer another opinion that aligns with teo_audio, which might encourage you to seek out a willing tech. The cost is substantial, so I encourage you to not give up quite yet.

Also, although you didn't solicit veterinary advice, anzaanimalclinic provided excellent information.

I haven't seen it mentioned on this thread but cats definitely do not like being left alone for extended periods. Maybe the delay you encountered contributed to the cats behaviour
I was once told of a couple that went on vacation for two weeks (and presumably had a "cat sitter' for the duration)
When they returned from vacation the cat immediately jumped on their antique cabinet, looked them in the eye and proceed to pee all over it

What you need (what we all need at times)  is an old school tech with reasonable prices..  As of course they are rarer than hens teeth.   My only suggestion is to call Northridge Electronics in Simi Valley ,  CA   and talk to Tom.    He has had and has I suspect numerous service provider accounts with major players over the years and is qualified and he has always been reasonable.    I have shipped to him just for his service even though I had lived in a major metro area and there were repair shops there.    Obviously  7k is  just a bit steep.     Hopefully he has not retired yet as hes getting close .