The Janome 6600 & 7700, and most Pfaff machines have built in dual feed. The Accufeed for the 6600 operates much like Pfaffs IDT does. Lift it up and back when you don't need it, swing it down into place when you do.
Recommend looking for an older Pfaff, their newer machines (post 2000) just aren't the same quality as the previous German-made Pfaffs were. I've heard this from SO many quilters & sewers. I also had a Pfaff made in 2006, and it was totally inferior to a Pfaff w/IDT that I had in the 90's - and was FOOLISH enough not to keep !! :(