Digital BW, The Print

Found this link on the 2000p group:
http://www.digital4to.com/

When I get some spare time I'm planning to try refilling the two black
cartridges with different black inks and do two-color BO printing with
PowerRIP. Can anyone give me some good recommendations on what inks
would be suitable for refilling the 2100? Are there some that would
work better than others? Any inks I should avoid? I was hoping to
achieve neutral prints with deeper blacks than the Epson Matte Black.

Thanks!