Digital BW, The Print

i just got a (rather used?) r1800. banding is not only at the borders, but anywhere. (although perfect nozzle test). moreover there are slight blotches in the middle/light greys or gradients,  using jettec inks (because i got it like this) and qtr. 

i'd like to go for mis- or cone-inks and a CIS. but i fear, the print head will not last long any more.

who knows about? 
would you dare buying a CIS for this printer, or rather for my epson 2100 which i bought as new 6 years ago?


christoph