The trial that comes with Cubase is not the Grand 3. It is the Grand 3 SE. This version only comes with three instruments. To get all the instruments in the full version, you need to purchase the full version. And as far as I understand it there is no upgrade path from the Grand 3 SE to the Grand 3.
iMac 27" Quad Core 8 GB RAM, OSX 10.7
Steinberg MR816, Motif XF8, Maschine, Cubase 6.5.3 / 7.03. Omnisphere, Stylus RMX, Komplete 8 Ultimate, Fabfilter Total Bundle, Sibelius