Digital BW, The Print

I have an epson 1280 using MIS GP color and eboni black.  Color 
results with downloaded profiles look great.  However if I try to do 
a duotone, tritone, or quadtone the results are awful.  Even if I 
convert a grayscale to RGB and apply some color to simulate a sepia 
tone the results are awful.  Heavily saturated with one color 
dominating even if I reduce the saturation to less than 10%.  Anyone 
have any suggestions?  Thanks

Joe