I have iPF8300, NEC SpectraView display and X-Rite i1 Publish Pro2.
You don't necessarly need i1Photo Pro2 to profile your iPF8400 - it has improved multisensor (spectrodensitometer), so the intra-instrumental agreement is very good (0.6dE on avg.) - all you have to do is to perform autocalibration on some of Canon OEM media, and use standard profiles provided by paper manufacturers.
i1Photo Pro2 may be useful to create profiles with perceptual rendering intent tweaked to your taste, or getting optimal neutrality on OBA loaded media under certain light sources, or for tweaking the colour rendering for a specific spectrum of a light source, but basically you get decent results with your iPF8400 out of the box.
At the beginnig you can buy PA241W without calibration solution, use NEC Multiprofiler to calibrate and profile it without sensor. Then you can decide if you need i1Photo Pro2 to tweak/improve printer profiles to your taste, and get SpectraView II license, or SpectraView II kit with NEC SpectraSensor colorimeter in other case.
On the other hand - I'm very happy with my i1Pro2 + NEC/EIZO + SpectraView II/ColorNavigator + iPF8300 combination results, so if money (+time for a lerning curve) is not a concern, I can highly recommend it.
Remember that you'll need daylight or high quality lighting to achieve color match, so you should also consider SoLux daylight light bulbs, or some of GTI lite / JUST Normlicht lighting solutions for evaluating the colors of your prints.