correct me if im wrong. but the Audigy platnuim, and the Audigy 2, have about the same quality sound.
the difference is i THINK Audigy 2 is Surround sound 6.1 (6 speakers. one front center. 2 front, 2 back...and the new one, in the rear center)
and audigy platnuim is surround 5.1
perhaps im wrong tho :P depends on what your speaker setup is going to be really. i have 4 speakers (simulated surround) with an Audigy X Gamer. which could if i wanted i think do 5.1 surround. but i never bothered cuz i have no place to put the extra speaker with my layout.