Digital BW, The Print

I bought a Canon i950 -- unfortunately before doing enough homework on 
B&W inkjet printing.  The printer is fantastic for colour, but I am 
unhappy with the results I get for B&W work (mostly because I cannot 
get *only* black -- the printer alwyas mixes photo magenta/photo cyan 
into the output).  It's good enough for proofs... but not much more.

What would you recommend that fulfils the following specification list:

	* Capable of printing on 13x19" sheet paper
	* Has pigment black ink
	* Is capable of TRUE black-only printing
	* Works with Mac OS X 10.2

I'm not interested in quads or somesuch.  I would consider using a 
non-manufacturer ink, provided I only needed a single ink (i.e., a 
pigment black).  I'm happy to stick to a single, matt paper, provided 
it is of good quality.

M.