To answer OP's last question, years ago I asked Steve a similar question and he said the DNA 125/225 were roughly on par with his B revisions of the older units. So that would make the Rev A amps a sizeable step up from the stock 125/225.
Might be worth asking Steve if modding your amp might make more sense than buying another stereo amp? Just a thought.
Might be worth asking Steve if modding your amp might make more sense than buying another stereo amp? Just a thought.