Hi Frank
For anything Jame Bongiorno designed I would only go to Michael Bettinger if possible.
http://www.bettingeraudiodesign.com/gas-audio/
Mike restored my Sumo 9 and it is one hell of an amp now.
I don't know if you are in the NY metro area but if you are I've had Scott Gramlich of SG Custom Sound do a lot of repairs for me. He is out in Douglaston Queens NY. Near the LIRR.
Here is his info:
40-33 235th Street
Douglaston, NY 11363
718-224-5083
Thanks and good luck.