I don't know much about GR Research but I once listened to him trash my speakers (JBL 4311) claiming the JBL engineers didn't know what they were doing, the crossover caused comb filtering, and other ridiculous assertions. Of course, at the end he offered a $700 crossover kit to "fix them".
He had no clue how those drivers and crossover were designed to work together. The gall to say the most popular studio monitors of their time were "trash". He may have a devoted group of followers, but he's really just a snake oil salesman trying to cash in on people's insecurities.