unfortunately, theC2 sounds like it will not have band 2 (which is the primary one for my telecom) or band 4 (which is the secondary one, and IS supported by the 10 III). band 5 is used by my carrier, but only in a single tiny area, from what i understand. also, my telecom (T-Mobile USA) is the only carrier that sailfish works on in USA.
it sounds like the 10 II+III (and IV+V eventually) remain the only choices for north america.