If you like the K3 inkset, the Epson 3800 is an attractive package that will give you a 17" carriage and also smaller cut sheet.
I have both the 3800 and the iPF5000 in the studio. Print quality is very similar. Only real difference to my eye for B&W is that the 3800 exhibits less bronzing on glossy surfaces than the iPF5000.
Another factor which may be important to you is that the Quadtone RIP supports the 3800. As much as I would like to see QTR for the iPF5000, I doubt that we'll ever see QTR supporting the Canon printers.
The 3800 is an interesting compromise, certainly. I'm heading into Palo Alto today to look at lights (whole other story -- I'm getting interested in shooting still life with my Better Light system, so I'm in the market for some kind of continuous lights), and I think they (Keeble & Schucat) had a 3800 in. Hmm, maybe I'll take my flash drive with me and armtwist them into giving a demo.
I do like the output from QTR, but I've probably not really played with it enough to have properly mastered it. I should give it another go really.
One thing I've always struggled with with the Epson driver (and the K3 inks on the R2400) is that I've never successfully made it print anything vaguely approximating what's on the monitor. With colour, fine, but with advanced B&W, everything is always way too dark. I eventually came up with a technique of adding a curves layer at the top of the layer stack, deleting the layer mask, then creating basically a gamma correction curve by clicking dead centre on the line and dragging that point up to the 75% point (assuming white to the top and right, black to the bottom and left). I use this, do a work print, then hand-tweak the curve slightly if necessary. As a workflow, it's annoying, but I have had some very good results from it. If anything, it's more like wet darkroom printing in approach, but it would be so nice just to be able to faithfully render an on-screen image for-once.
I did put a lot of time into trying to find a solution, before I went for my belt-and-braces approach with curves. Whatever combination of printer and image 'colour' profiles I chose, I always ended up with something way too dark. The settings in the printer driver didn't help either, because they didn't have enough adjustment range to provide enough correction. This is all using Photoshop CS on Windows XP with the current version of the Epson drivers.
QTR didn't have the same issues, but I basically was using profiles I made myself for it (mostly by eye). I didn't get as far as making profiles that correct for the sepia tone of the K3 black inks, however. Maybe I'll dust it off and have another go at it. I'm tempted to try the Cone inks anyway, though I'm wondering if they are aimed more at softer-toned images and matte papers, so I'm not sure if they will really work with my kind of visualisations. It can't really hurt to try it, of course!