Hi all,
The Roland 5050 has two slots for expansion cards (the new SRX's only) and you can get an excellent preview at http://www.rolandus.com/Multimedia/Flash/srx/srx_demo.html .
Click and hold one of the cards and drag it over to where it states.
The two cards I have are the Complete Orchestra (6) and the Complete piasno (11). Very pleased with both.
Keith