Also do not rule out the Roland/Edirol
SC-8850. While it is not expandable, it
is very comparable to the MU-128.
Also, you should realize that both these
modules use RCA outputs instead of standard
1/4" jacks. So, if you use them for live
performance through a PA system, be aware
that the signal is not as "Hot" as the 1/4"
and therefore the volume will need to be turned up much higher(thereby "possibly" creating noticable noise).