Based on your lengthy discussion, I agree that something needs to be resolved. I had a problem with my DSP5500's when I first bought them, but they were used, but still under warranty and I bought them from a local dealer/service center at the time as the previous owner upgraded to the DSP6000s. Mine had that crackling noise too, but they just took the back panels of both speakers and replaced them and the problem was solved and never had a problem since. I don't know what causes these problems other than maybe a brown out, faulty components, etc. But Meridian is supposed to be using high quality components and the boards are supposed to be tested using sophisticated testing equipment. I wish I had an answer to your problem. If I was in your situation, i would pack everything up and deliver it personally to the M UK manufacturing plant and have them inspect it, repair and replace as needed while you wait. Unfotunately, that's a lot of money and time to invest, but maybe that it what is needed and maybe have Meridian reimburse you for your expenses.
I really hope things get resolved. I hope for the customer's sake and that of the company that issues get resolved quickly to promote excellent customer service. I feel top end mfg of audio equipment should have the best customer service, we are paying a premium for high end equipment and it should perform as such.
Customer service can make or break a company. With audio equipment, there are so many different ways things can be set up which can complicate things. As soon as we connect Meridian gear to another mfg, that's when they have little control and it is frustrating, I eish you the best of luck in getting things resolved.