Does the 6400 use matte black ink when printing onto lower end matte paper such as Red River Polar Matte which is not a fine art paper like Canson BFK or Arches? My experience with the Canon Pro-1 is that this printer uses Photo Black when printing on lower end matte papers and only uses Matte Black when printing on Fine Art Papers with that 35Margin border.
I have had real clogging issues with Epson printers and hope that the Canon 6400 will give me the beautiful black I am used to from Epson but eliminate the clogging and ink changing between Photo Black and Matte Black.