I have the Janome 6600 (which should operate the same as the 6500 when FMQing) and I was told that I could use the open-toed plastic darning foot for FMQing (it came with the machine) with no adjustments or the metal circular FMQ foot (purchased separately). However, when using the latter it's crucial to set the height adjustment correctly (trial and error???) or else the thread keeps breaking.
My dealer (50 miles away) not only doesn't make house calls, but likes to charge for everything and/or upsell me to another/different machine. You have a dream dealer :-)