Looking at either Hex or M5 series subs and I walked into a store and the guy said he wass shipping back 25 pairs of M5 subs, said they were disconnecting from the cone. Could this be, he showed me, but maybe he was trying to sell me the hex series and was sending them back for his own reasons.????

Get Boston Pro series subs to go along with Diamond Hex or M5 tweeter/midrange speakers. I haven't heard about the problem you mention....