Maybe I will get lucky with the digital clamp meter. Following e-bay address has multiple clamp meter auctions from the same guy (first example is around the fourth or fifth item on the page with subject as follows: Digital Clamp Meter, 1000 Amp, No Reserve, $1.00):
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=42291&item=4384170357&rd=1
Picture and description look/sound like $150 meters. He has over 6,000 e-bay sales with 99.7% positive feedbacks and has sold these meters before. That's why I decided to take the risk--not to mention that even if it is a "ripoff" I haven't lost much.

Ratpack/bugbitten: Thanks for the info on the "inrush protector". If after measurements, my amp isn't out of spec for the 755, the protector could be the answer. But it definitely sounds as if I'm not the only one suffering from "thumps/blinking lights".