The MKS-20 is the same thing in rack form if you don't need it for a keyboard but still want the sounds. As for selling it I wouldn't want to deal with shipping on that so you might try local Craigslist. There was one here a few months ago in good shape and they were asking $700 I think.
I have a Roland RD 1000 that I also purchased new. I have recently lost all my sounds and need to borrow (will pay) to use someone's sound card to re-program this piano, which I absolutely love. When I moved I misplaced the owner's manual and the card. Roland is no longer supporting this piano and I am at my wit's end trying to get this fixed. Is there anyone out there that can help me? The piano is at the music store and they are willing to accept responsibility to get the card to them and back to the rightful owner plus pay for the use.