I also print on an Epson (alas 3800) and always wonder if the color setting in the print driver (you use black/grey) would make a difference. I imagine if it would use black but mix a bit of cyan inside, it might be more dense? in a test print, I couldn´t really see a difference on the film judging by eye sight..
I could see a difference when I printed a vector in "rich black" vs 100%k black.