The center cluster is by a company called OAP.
I believe it is from their Q series, but I'd have to get a closer look at them. I'll see if we can pull out the big ladder sometime soon and get a good look at them.
The center is being run off of one side of a QSC RMX 1450 power amp, and I have it high passed at 100Hz using the board EQ.
OAP builds perfectly reasonable speakers. I have only ever come across a couple installs, but both performed fine. Those are probably not Q series as it looks like they have handles on top. Judging by their size perhaps they are http://www.oapaudio.com/index.php/products/flyable-installs/item/t-1502?category_id=55
I picked these because they are a biamp only example, where a standard speakon(pins 1+ and 1-) will drive only the 15 woofers. Maybe they are a full range model and one or both horns are toast?
1) Get the cluster sorted out. Less posting more investigation and analysis. If you aren't comfortable with this stop and beg the leadership to bring in a professional.
2) Split your signals! Instruments will go into the JBLs. Vocals only into the cluster. Go back to driving the sub off an aux. Keeping the vocals separate from the instruments will improve intelligibility as you avoid IM distortion. http://www.youtube.com/watch?v=HO3XZnDkYfE
3) Configure the JBLs as dual mono but leave them off to start.
4) Nothing but kick, bass and keys in the sub. Add them in that order one at a time so if the low end falls apart you know what to investigate.
5) You may find that with the wedges on, vocals only in the cluster, and the sub running but the JBLs off that the instruments are already a big muddy loud mess just from the stage wash.
6) Create and enforce a stage volume limit. No sense even turning on the JBLs for instrument reinforcement if the room is already too excited.
7) Once it sounds decent with just the backline, wedges, cluster and sub then and only then fire up the JBLs. Start by bringing up the level of whatever is too low in the wash from the wedges and backline, this is usually the keys, add in any other instruments that need more level to be balanced in the room one at a time.
7) Eventually you may want to switch the JBLs back to a stereo configuration and pan things appropriately one can then pull SMALL amounts of certain instrument signals say guitar or keys in to the cluster to anchor them.
If things fall apart go back a step and investigate what happened.
There were plenty of good mixes long before IEM became the must have thing, but those mixes where made by engineers that understood how to manage and work with the stage levels.