  We construct pi-pi amplitudes that fulfill exact elastic unitarity, account
for one loop Chiral Perturbation Theory contributions and include all 1/Nc
leading terms, with the only limitation of considering just the lowest-lying
nonet of exchanged resonances. Within such scheme, the Nc dependence of sigma
and rho masses and widths is discussed. Robust conclusions are drawn in the
case of the rho resonance, confirming that it is a stable meson in the limit of
a large number of QCD colors, Nc. Less definitive conclusions are reached in
the scalar-isoscalar sector. With the present quality of data, we cannot firmly
conclude whether or not the Nc=3 f0(600) resonance completely disappears at
large Nc or it has a sub-dominant component in its structure, which would
become dominant for a number of quark colors sufficiently large.
