Digital BW, The Print

MIS Quadtone VM on Epson Archival Matte via Roark curves (for epson 
1270), printed on an epson 870.

I recently installed these inks and though I'm really happy with the 
overall quality I wish I had deeper blacks and better tonal 
seperation in the lower midtones.

I tried using the epson black ink with the MIS quadtone "color" 
cartridge and at first look I get the black density I was hoping for. 
However, on closer inspection I see black dots and very high contrast 
in the lowest values, which is undesirable.

Anyone been down this road? Any suggestions for getting deeper blacks 
with the quadtones without the artifacts?

Thanks