I do not have any Spitfire products, but:
a) Nektar P1 primary a DAW controller. And it does not support Sonar. You can use it as a simple MIDI controller, but you loose the most of its functionality (and so the money you pay for it).
b) Spitfire products are Kontakt instruments, so the best way to control them in general are NI (NKS compatible) devices
c) general CC writing can be done with any simple MIDI controller, by proper type of hardware control. I mean depending from the target parameter, that can be Modulation Wheel, Knob, Fader, Pedal, After-Touch, etc. Note that there is a difference between simple "knobs" (270 degree, with current position indicator on it) and "endless encoders" (can be turned endless, sometimes with LED ring/display/bar indication for current position). General CC is much simpler to record with a simple knob: it has all possible (128) positions within 2/3 of a turn. Endless encoders normally have less "ticks" per complete turn, so operating is coarse or fine (depending what change in parameter is set for one tick), but not both at the same time. The advantage of endless encoders is they can be always "in sync" with corresponding parameters, so you do not have to sync manually (as with simple knobs). But that should be supported on software and hardware level. I am not sure how CC recording in Sonar is working with NKS encoders, may be someone with S keyboard can clarify that.