I've gotten some Soundcraftsmen shoeboxes that looked like they lived a tough life, but only one of them ever disappointed me. I should have checked it as soon as I got it, but it was a reserve amp for a future project, and by the time I checked it out I'd already had it for two months.
One channel worked; one didn't.
I gave it to my son when he visited from Ohio last year. He wrapped duct tape around it like a handle and carried it on board the plane home. He's been using the good channel to run his subwoofer for over a year.
It's always a gamble, but five out of the six amps that I bought worked fine and were within spec, regardless of appearance.