I second the positive opinions about Cones K7 and the HP Vivera inks for black and white imaging.
I would have to agree that the Z3100s use of neutral gray pigments, which allow smooth monochrome printing to be possible on gloss fiber papers or matte rag papers, WITHOUT having to use light magenta or cyan color inks in the mix, is superior to Epson K3. They also are designed to fade overtime at the same rate and not color shift in different parts of the tonal scale. These HP inks also have less gloss differential issues and bronzing issues. I find the Hahnemuhle Photorag Baryta to be the best paper out there of this kind, with Ilford Gallerie Gold to be second and Innova Satin third. And, I used to use the Innova Ultrasmooth, what is essentially what the Epson Exhibition Fine Art is. Of course people who work for Epson will tell you differently. They always do and they always will. They want to dominate the printer, ink, AND media market as well as the PR market.
Secondly Jon Cone's K7 carbon based pigments of 6 or 7 channels, all the same hue of beautiful monochrome, are superior to the Epson K3 in tonality, by a long shot. And, far more subtle in the high-end especially, than HP Vivera or Canon Lucia or K3, vivid or not. The K7 heavy carbon load makes them unsuitable for gloss fiber work in my opinion but that is not their market, or their focus. The K7 matte rag prints are more three dimensional than anything I've ever used via inkjet, and are truly outstanding. Cone deserves an international award of excellence, and often receives precious little well deserved praise from people who should know better. Only someone who doesn't use K7 regularly and/or works for Epson would suggest that they clog or would void the warranty of your printer. I have had the Neutral tone set and the Carbon Sepia set installed in three different printers for 3 years and they don't clog, ever. Epson K3 and Ultrachrome are the worst cloggers of all time and an industry disgrace. Truly. What a waste the Epson inks were in having to deal with all those perpetual head cleanings. I probably spent at least a grand or more on wasted inks from doing all those head cleanings , not to mention the lost time in doing hourly nozzle tests.
Oh, by the way DO check out Henry Wilhelm's website regarding the sad state of permanency with Epson K3 inks on the Hahnemuhle papers that was recently posted. There is nothing wrong with the Hahnemuhle papers, they are fantastic and test great with the Vivera inks and many other inks. Just Epson's lack of k3 permanency is of real concern here. Of course Epson and their reps will tell you not to use ANY fine papers other than their own. What would you expect them to say, they want it all. They will not receive it from me.
I've said it before. The first printer I've used that could make B&W print indistinguishable from what I produced in the darkroom (actually better with digital control of the image) is the HP z3100. And that B&W quality is why I purchased the printer.
21 months later, I'm printing, selling and getting more B&W prints into shows than ever before. YMMV