Musical fidelity M6SI problem.

I missed this note.  Glad to hear you are happy.  It is a heck of a good amp.  I do think the M6 phono stage is a big step up but if you are happy with what you have...awesome!

I am a dealer for MF.  I have never had a customer have that issue as described.  
Regarding customer service, that is defined by your dealer.  I had a customer with a warranty claim.  Focal Naim NA (the distributor) quickly provided me a service center nearby the customer.  The service center was slow, but that was more that they couldn’t replicate the issue which turned out to be wonky issue with a particular turntable.  
FN NA paid for the service and return shipping.  Was not an issue.  If you have customer service issues these days, it is solely an issue with your dealer.  

MF has switched distributors from that time period.  That does make a meaningful difference. 

Don't get me wrong, you are still subject to the customer service associated with service centers as they have a contracted network.  But that is a challenge with all manufacturers.    

Ugh...they had a delivery that came in and went out only covering a fraction of backorders. I was told 16-18 weeks recently before they will be getting next shipment of M6sis.  I gave full refunds back to two customers because I am not going to even try and hold money for 4-5 more months.  

I can't say I have ever spent time with a MOFI table.  The M6x is very flexible and should be a good match with most cartridges.  It is also fully balanced and that is a huge benefit with MF in the M6 range.  You almost always get the most out of MF gear when the signal chain is fully balanced.