Hi All! I found the replacement amp for the Thiel SS2 subwoofer. Rob told me a BASH S500 would work. https://www.parts-express.com/Bash-500S-500W-Digital-Subwoofer-Amplifier-300-752?quantity=1
It isn't the same exact dimensions so I will have to make a custom ring or gasket for it to fit on the back of the sub. If anyone wants a broken SS2 amp for parts, please let me know.
-Brian