Thanks, guys. I appreciate it. I'm not sitting around all bummed about it. I got the trigger to work about an hour ago - it was just the cable that I was using. Plus, I have my fancy new speaker cables to keep me warm.
The popping isn't like a 90dB thing. It's certainly loud enough to notice, though. It doesn't do it all of the time, and sometimes when it does, it's quieter than other times. At least at the moment, when it's turned on and off by the trigger, the pops are very quiet. When I push the power button on the front, it tends to pop louder. Odd to me, because the power button and trigger both put it into and out of standby mode.
I will contact the seller. He may or may not have sold it without divulging the pops - he might never have noticed. For all I know, he never used the amp. However, I will mention this to him and work something out.