There are 3 versions of amp boards.
The last version is best, any version can be upgraded to the last.
There is a service bulletin mod that should be done if not done. They can set themselves on fire if things go wrong.
They are nice to work on, amps come out easily.
There is no DC offset as factory built, one can be added easily by a handy tech.
There is plenty of documentation for service online.
There is no speaker protection. They are powerful enough to set your speakers on fire if things go bad.
They can be bridged to get 1000 Watts.
They weigh 80 pounds and have sharp heat sinks on 3 sides. Gloves recommended or care when moving them.
They sound awesome and look hella cool.