George and Rick,
Thank you for your input. I downloaded the DGX-620 manual and already read it.
I am curious to try on such keyboard.
Starkeeper, the special voices are:
Live! Grand Piano
Live! Warm grand piano
Cool! Galaxy elecric piano
Cool! Suitcase electric piano
Cool! Electric piano
Cool! Rotor organ
Sweet! Tenor Sax
Sweet! Soprano Sax
Sweet! Muted trumpet
Sweet! Pan flute
There are a few XG voices that are not present on the DGX-305/505.
The styles, like the older DGXs, have only 2 variations.
I hoped for a sweet harmonica or oboe voices, or a spanish guitar voice. Such voices would enrich my compositions. It seems that yamaha have (still) reserved them for their more expensive boards.