Update on the Kustom: Noticed the volume level fluctuating once or twice -- thought it might be a late-manifesting effect of the aforementioned "toast". Didn't take it in to a tech, but I did pop the top and couldn't find anything burned, burst, or discolored. Thought it might have to do with the much-earlier-mentioned ribbon-cable issue some have encountered with the amp (namely that the connection might have been dirty or slightly corroded, but that unplugging and plugging in the cables seemed to address the issue). Unplugged all of the ribbon cables and cleaned the prongs of the contacts with a cotton swab lightly sprayed with DeOxit D5. Plugged them back in. (Cleaned the pots while I was at it -- volume had become slightly scratchy.) The amp has worked flawlessly since (this was a month or more ago). There is still a bit of slowly ebbing, residual doubt regarding the amp but, from everything I can see, it's working fine and seems set to continue doing so.