I am wondering if one of the mosfets in the amp has gone bad due to being over driven a little when the new radio was hooked up to it.
if you are thinking about getting a new amp I would buy a high drive amp. RM makes a amp I think is a 503 high drive. less chance of blowing it up with a single final radio that hits pretty hard. I have a few amps but just a fad when I bought them . tried them a few times than just put them in my closet.