peter wrote

Belt sanders and ROSs sometimes overlap in their uses but are
not completely interchangable. They are two different machines for
two different uses.

ACK.

If you expect a ROS to take material off with the same speed
as a belt sander, you will be disappointed. If you expect a belt
sander to do as smooth of a job as a ROS you will be disappointed.

There's this Festool Rotex 6" ROS which combines preliminary sander,
fine sander and polisher. I never used it but it gets excellent
comments, for example
http://www.festool-usa.com/portando/...ten.cfm?id=325
http://www.woodshopdemos.com/fest-14.htm

BTW, a good 6" ROS will require two hands most of the time
also.

I have a Festool ES 150/3 6" ROS and use it with one hand all the
time. It's an great tool!

Feel free to contact me for any specifics.

Regards,

Christian