B&W Nautilus 804s and clipping


Hello there - this is my first post and I'd be grateful for any help you folks can offer me.

I'm building my first home stereo setup right now after years of waiting. The first component will be a used pair of B&W Nautilus 804s which I've found for a pretty good price.

My question is this: how can I tell whether the speakers have suffered somehow due to clipping? The reason I'm worried is that the guy I'm buying from has been running them off a Harmon Kardon AVR-3000 receiver (with 50W output in stereo mode). Isn't this likely to have caused some damage if he's been working the amp too hard? If so, will the tweeter etc. sound noticeably different from normal or will they just completely fail to produce sound?

I was only able to audition them using his amp, not having yet bought my own. Is it necessary to hear these with, for example, a power amp to know whether they are in good condition sonically?

Sorry to labour the point(s). Hope some of you can help!
borntorun
borntorun
When testing the tweeter be sure to feed the speaker a signal that will truly test the tweeter. B&W sets there crossover for the tweeter rather high for the 800 series floorstanders. All vocals and 95 percent of the fundamental frequencies from classical music are actually handled by the midrange. B&W does a pretty good job of integrating the midrange with the tweeter but if you divert your ear from the midrange (i.e. hold a piece of foam or some other absorbing material at 90 degrees to the cabinet just below the tweeter and listen directly (close up) to the tweeter, you can find the source material that will be a good test disc. You may be surprised. Rock music with high end guitar riffs is the easiest source to test the tweeter,or a test disc with a range of tones. Of course once you find the proper source material then increase the volume and move back. If the tweeter is damaged and still 'works' you will hear it at high volumes -likely as a very noticible intermittent 'rasp' it will be obvious and will not require any guesswork. Just be sure to listen to your source material on a known good system beforehand. Much more common for the top mounted tweeter is damage that can be observed by careful visual inspection, tykes and inquisitive adults have a habit of 'pushing the button' - jamming their finger into the tweeter.
Thanks again for all the help. I'm now running these with a Musical Fidelity A300 and they are sounding great. There are no problems at all with the tweeters but, yes, I have noticed that they are not given much work to do compared to the other drivers.

Currently deciding on the best-sounding speaker cables and planning to buy a Rega Apollo pretty soon...