Hi Keith,
I'm only a hobbyist so I don't like recommending stuff to proffessionals.
Bernie has recently also purchased one of these modules, so maybe you could get his opinion as well. He uses a controller keyboard.
http://www.synthzone.com/ubbs/Forum43/HTML/000064.html

I personally don't think the quality of the sound is quite as good on the sd2 as on my sd1+.
( Comparison wise, it would probably be like comparing psr1500/3000 to the sounds on a Tyros 2)
but I think it's a great little unit.

One of the guys on solton group purchased one for his Tyros 2. (thomusic) http://launch.groups.yahoo.com/group/solton/

I think he may have had some hassles accessing the higher banks in realtime

Ketron uses
Controller 0 for bank changes
wheras

Yamaha
Controller 0
Controller 32 for bank changes

yesterday he was checking out this little
controller module.
http://www.behringer.com/BCN44/

best wishes
Rikki