It's an old topic, but for anyone interested I would recommend the Virsyn Matrix and the Xils-lab Xils V+ (based on the Roland VP330 vocoder plus), two quite different types of vocoders, but very good in their own way,- the Matrix is used by Kraftwerk and Karl Bartos (ex-Kraftwerk) by the way.
If you happen to use the FL Studio, the Vocodex that comes with the DAW is quite nice too. :-)
Asus PC with Windows 8.1 - 64bit., 16gb RAM, IntelCore i7 3770 CPU 3,40ghz.
FL Studio 12 Studio Edition
Akai MAX49 Midi-keyboard
V-Collection 4&5, Xils 4, Xils 5000, Xils V+, Xils PolyKB 2, Blue 2, Blade, Eiosis AIREQ, Slate VTM, Largo, Lector, MiniMonsta, Nave, Korg MonoPoly, Syn-X, Stix, Bazille