My concern is they have a manufacturing recommended power rating of 300 w and the owner was using Pass x 6oo's to power them.given that the manuf has a higher power rating for them & that the owner used X600 to power them is a very good thing (as Mechans has already written) as this means that the amps most likely did not clip the speakers. Clipping does more damage than playing loud/very loud as the distortion created by clipping gets past the x-over ckt & destroys the drivers - tweeters first. Using an under-powered amp would have been the worse option.
And, it looks like the Andra2 like to be played loud guessing from the manuf's rating.
I recently auditioned used eggleston works andra 2 speakersdid you take your own music to the audition so that you could listen attentively to passages in your music that you now know very well? If not, you should have! The whole point of auditioning is to see that the new potential buy is better than what you own + that the speakers are healthy as far as you could tell.
Speaker drivers are very hardy & quite tolerant of abuse as long as the amps don't clip for long periods or often. If the drivers are getting abused frequently then the drivers are likely to show this when you listen - uneven SPL from left/right which will move the soundstage right/left, buzzing from the cone driver & maybe some physical damage on the driver upon close-up inspection are some of the tell-tale signs.
Simply playing a speaker loud is not sufficient grounds to reject buying it. If it is, then, cough up the money & go buy a brand new speaker & put your own volume/SPL signature on it. Speakers are meant to be played loud esp. if you get into your music & are having a good time listening.... According to me, no point in buying an Andra2 pair of speakers & then playing it at 70dB SPL! I want that room to rock when the Andra2 are playing....
hope that this helps.