I've tried all the versions of Shuguang 845s. I like the 845Cs best. The 845Ms were reputed to have problems, but mine kept going for 2 years. The Ms and the Cs - both metal plate - have a similar sound, with the Cs being a little more transparent. The 845Bs are warmer and less detailed, and could be just the thing for toning down a system that's a little too much on the bright side. Cryoed 845As sound better than the stock version. They're bright by comparison with the other models - too bright for my taste - but could be good for putting life into an overly warm system.