  New integral field optical fiber spectroscopy obtained with the INTEGRAL
system, together with archival {\it {\it HST}} WFPC2 and NICMOS images, have
been used to investigate the ultraluminous infrared galaxy IRAS 17208$-$0014,
one of the coldest and most luminous objects in the IRAS 1 Jy sample. The 2D
gas velocity field identifies the {\it optically faint} K-band nucleus as the
{\it true} dynamical nucleus of the galaxy, and shows that the 3 kpc, tilted (i
$\sim$ 35 degree) disk is rotating at $\Delta$Vsin$i$= 250 km s$^{-1}$. The
kinematical, morphological and photometric evidence presented here supports the
idea that in IRAS 17208-0014 we are witnessing a luminous, cool ULIRG which is
at the final coalescence phase of a system composed of two spirals with m
$\leq$ m$^*$, a mass ratio of 2:1, each consisting of a disk+bulge internal
structure, that have been involved in a prograde encounter. This system will
most likely evolve into an intermediate-mass ($\sim$ L$^*$) elliptical. The
multifrequency empirical evidence gathered so far shows no trace of a luminous
QSO, and indicates that starbursts dominate the energy output in this galaxy.
Therefore IRAS 17208$-$0014 questions the universality of the ULIRG to QSO
evolutionary scenario proposed by Sanders and collaborators, and supports the
one recently proposed by Colina et al, where two low mass disk galaxies would
produce luminous cool ULIRGs that would not evolve into a QSO phase. (abridge)
