Angelo,
Right. The EVs need a preamped signal (except for very small venues). If your PA head (powered mixer) has a monitor out that should work. One other setup I use with the 9000 Pro is a Roland Cube keyboard amp that has an output jack marked (Pre Out). I point the Cube at me for monitoring and send a signal to one of the Evs then "daisy chain" the second EV to the first one via the XLR in - outs. This of course is mono only. However, The little Behringer (costing less than $70.00 new) has proven to be a practical solution when I use the keyboard's (X1) built in speakers for monitoring purposes.
DVJ