I've been a Piezography user for a number of years, first with the K7 and now with the Piezography Pro inkset, but I've only had 17" printers (4800 & currently a P800), one of which has always been a dedicated B&W printer. If you are converting your printer from one that used color inks, then I would HIGHLY recommend the Piezo Flush to clear out the lines before you install what every flavor of Piezography you choose. You can, of course, install the ink right away and go through a number of cleaning cycles to clear out the existing ink, but the ink is Way more expensive than the flush, and you'll go through a lot of ink. Also, the carts you use for the flush can be reused when you want to clean the lines and/or dampers periodically. You have to consider this (purchasing the flush and carts) as a one time cost. Ink & Paper on the other hand....
I have always had a set of carts with Flush along with a separate set of carts with only ink. If you get the chance, since you're in the NE, I highly recommend one of the Piezography workshops in Vermont with Jon Cone (inventor of Piezography) and Walker Blackwell at Cone Editions. If you care, there is a Youtube video of Jon creating a print on a 9900.