Sounds like bad power caps to me. There is a reason the transformer gets hot...and in my experiance, it's not that the transformer has gone bad, it's nothing but some iron and some wire. But the caps...now those have limited life, go bad and cause problems. Look for the cause, not the effect. What breaker pops? The house breaker? If so, you probably do have a smoked transformer....caused by bad caps.
This site has lots of info abou the amps including schematics and many many postings about transformers and part. Search this site and you will find nearly everything you need...except possibly the money to pay for your Sunn habit. There is a correct 200S cabinet on Ebay right now, ends in 5 or 6 days. Somewhere on the east coast I think.