I also think that the LS50s need high end gear to sound their best. I bought them over to a friend's house, and we hooked them up to his his VPI>Pass Labs>ARC chain, and they sounded amazing. It was hard to believe that they only cost $1000.
However, many people bought the LS50s to replace their $500-$1000 speakers and then hooked them up to entry level amplification: AV receivers, lower powered bargain integrateds, etc.. They didn't really get the full measure of what the KEFs can do. Hence the many pairs that are up for sale.