No wonder you're confused! So many different opinions (justified, of course).
Personally (my opinion), I have just had 4x Pirelli P-Zeros (Rossos) N4s fitted on my C2, directly after a full alignment.
My logic was that I wanted the "best" N rated tyre and personally wanted Pirellis as they had served me well before (P6000s, recommended fit on my previously owned SC, for instance, transformed the feel + handling).
The old tyres on the C2 were Bridgestone SO2s on the front (N2) and Pirelli Assimetricos on the rear (N3). These seemed OK, but the fronts were worn enough to be "tramlining" quite severely... hence the align/tyre route.
I would recommend having a proper alignment and a set of these P-Zeros... they have transformed the already marvellous handling to a new level.