anyone up this late? need advice on buying used power amps what signs to look for

I am meeting someone today to look at two nice power amps. I am not that familiar with buying power amps and don't know what to look for. these are a good deal if it works. they claim it works. can you give me tips on what to look for and check.

sorry for writing this so late I meet the person after 1 in the afternoon sometime. I am suppose to call after 1 to schedule a time

one amp is a nad the other is a rotel

any lights on the amp of a certain color to look for? should i make them crank it loud to see if it goes into protection mode?