Gene,
I am a dealer in Southern California and I ship all over the country. I've been selling Solton/Ketron since 1984. I'm very familiar with all their products from back then and currently.
The biggest reasons for me to buy the SD3 over the XD3 would be first, the polyphony. The SD has 128 and the XD3 has 64. Next, the 16 buttons on the lower section of the SD3 module let you select registrations for the first time where the names show up in a list of 16 at a time so you don't have to memorize numbers to remember what you are looking for for a specific selection. Also, these buttons can do all the same things that you had to do on a pedal board for the XD3 or your MS60.
The sounds are also better for instruments like acoustic piano, etc.
The other big new feature is the "riff mode" which allows you to pick a key and the SD3 will play chord progressions within the key you've specified.
You can buy the SD3 stock, with just a floppy drive, or with an optinal hard drive and vocal harmonizer for singers.
My price will be great.....just give me a try!
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George Kaye
Kaye's Music Scene
Reseda, California
818-881-5566
www.kayesmusicscene.com