I sold my 6600 to my Mom and I replaced her with a Juki 2010 (same size, I think as the Brother 1500). The extra height with FMQing is wonderful! And I have an Elna quilters dream that I can use for decorative stitches which is almost never!!
I have a Arrow table and the 6600 just barely fit in side to side. There was some extra space in the back of the machine, but not enough at all on the sides...
When I put in the Juki I bought an insert and it's perfect now. So the Juki is slightly smaller west to east and also smaller north and south than the Janome 6600.... I'm not home so I can't measure my machine.... I don't have the same table, but if the brother is the same size as the Juki 2010 (which I think it is or close) I would say it would fit no problem. But does Jamone make inserts for machines that aren't their own? How are you going to fill in the gaps? I really really like my insert- it makes FMQing sooo much easier!
BTW- changing the bobbin is a breeze. My machine stays put, and I just slide the insert to the left and access the door that way.