Al,
the RD 700 SX is an improved version of the RD 700, in that it has both the same piano as the Fantom X and a brand new piano, found also in the SRX 11 card.
_________________________
Korg Kronos 61 and PA3X-Pro76, Roland G-70, BK7-m and Integra 7, Casio PX-5S, Fender Stratocaster with Fralin pickups, Fender Stratocaster with Kinman pickups, vintage Gibson SG standard.