Maybe it's just that kid A and ok computer were just ripping off people who you'd like, and the rest of their garbage was ripping off people you wouldn't like?
You want something with the right voltage rating, and a higher amperage rating than the device specifies, generally. But 12v .333a is 4 watts, not 5...
It sounds great. There may be a relay issue, it's taking forever for the muting circuit to shut off on powerup, but I didn't spend a lot of time at the meet worrying about that. I'll check it out when I get the amp set back up in a few days.