i don't know how much i can help you but i can tell you a bit about canvas printing. i'm sure there are a lot of guys here that have much more experience. i'd say if you are getting the 9890 for canvas, it's a bit too much machine for just canvas. canvas at medium resolution looks almost identical to high resolution because of all the textural shadowing and dot gain. also the dmax can be sometimes lost on canvas so a machine that is searching for that last 10% of image quality will not be able to reflect it's capabilities in canvas.
so...the 9890, from what i know would be great for canvas, but of course it's main use will be printing large format photography and giclee reproduction. i'm not sure why they make a k3 (9890) and an hdr (9900) seems like the hdr inks do everything that the k3 does and more.
also, i wish i could find the page, but a lab did a very very extensive study on ink consumption comparing the 9900 to the ipf8300. the epson, when printing used from 40-70% more ink in all categories. that's not to mention all the cleaning cycles and head purging everytime you turn on the machine. i'd imagine per square foot, it's should be higher. so not so great a machine if you are planning on printing every now and then.
i think it is a better machine. kind of the bmw of the 44" range. very smooth quiet machine. i'm split between the 9900 and the ipf8300 for my next printer. the canon would have it if it had a better sheet loading set up (loads from the front by way of firmware...booo. that's insane. you can jam a 5' piece of paper into the front. but then the epson loads from the "top" and shoots the print southward. very strange. basically a good set up for a tiny 22x30 piece of art paper. but not for flatbed sheet feeding.)
in the end, i'd look at the canon before making a decision (and the hp z3200, $2500! @ 44"). a printer is supposed to make you money. the canon can be bought for $3300 (canon is dumping them to steal market share). it comes with 12 330ml carts, and all the software you'll need for basic ripping. and it will over time "make" you more money with less head clogging head aches. and as far as head aches. that epson's dx5 head will be periodically crashing into that canvas when it buckles. if the head is damaged it will cost $850. a damaged canon head can be replaced for $450. with no technician needed. also the canon is insanely faster. and remember with estimating speed comparisons, you will probably be printing at 720x720 8 or 16 pass (maybe 1400 x 1400, never 2800). any more resolution will not be evident on canvas. on and one more up for the canon, it's photo black and matte black are installed, not switched by a function. so you could switch between photo paper and canvas on the fly.
). clogging: yes there is. from time to time. not bad but it is there a few lines missing sometimes. i was canceling the auto head cleanig to avoid ink waste so, from time to time i have to print a nozzle check, not a big deal. a pain in the %^$ is also the maintenance tank, but , fortunately there is a resetter for it too.