Back when I used seperate amps I had all Haflers, (P500s, P230s ) heavy but tough as nails. I built 3 of them from kits, never a problem with any of them.
BTW they were suck in on the sides, blow out the back cooling, did have to be careful mounting them to make sure cool air could get in. ( I cut holes in the rack sides and put foam around the inputs) Always thought that was a strange design on the P500s.