Use an insert cable for the BBE to the Main Insert jacks on the mixer. You will need 2 for both L & R channels. Like these:
http://www.bhphotovideo.com/c/product/1 ... le_to.html
Plug the 1/4" into the mixer & the XLR into the input/output on each channel of the BBE. The BBE, don't overuse it. This is a common mistake people make which can yield in a harshness in the high end. It's not really designed to be an eq, it's frequency aligner to help project the signal to the speakers better in a live situation.
Take the Main out on the mixer & run to the inputs on the amp.
The speakers are rated at 400 watts program, the amp will push 525 watts into each speaker, a little more than required but as long as you aren't puching them into the stratosphere volume wise, you should be fine.
I would use the 266XL on the mics only (don't confuse it with the BBE - totally different processor), again you will need an insert cable for this. There are only two channels on the compressor so you will only be able to compress 2 mics. 2 cables like these:
http://www.zzounds.com/item--HOSSTP20
Plug the single end into the mic channel insert jack & the 'tip' plug to the input on the dbx, the 'ring' plug to the output.
I would set the compressor settings to a basic starting point
Threshold - -10
Overeasy button pushed in
Ratio - can vary anywhere from 2:1-4:1
Between the attack & release is an auto button - push this in. For different singers it will automatically adjust the attack & release.
Output gain - start at 0 and adjust accordingly. You want the compressed signal to be about the same as the non compressed signal volume wise when the compressor is bypassed.
Don't worry about the expander/gate section, just leave those fully counter clockwise.
If you use the USB interface on the mixer, then you won't need the Fast Tracks, however you may find the external sounds better - try both ways.
USB interface, plug the USB into the computer to the interface, the RCA outputs just plugs into the stereo channels of the mixer.