Cosmic Dreamer
As i wrote some weeks ago in this forum XVs have 128 voice oscilators driven by mono and stereo samples. In case of stereo samples XV uses two oscilators and the actual polyphony is 64. It would be nice if XV had 128 x 2 = 256 voices but as you understand their cost would be much above 3k. Roland uses 24 bit D/A conversion so the DSP/CPU load is already too high.
When you use old JV expansion cards (MONO)then you actually have 128 voice polyphony.
BTW XVs is the only synth that uses 128 true voice engine plus stereo samples and 24 bit circuitry.