Thank you all

UNCLE DAVE You know my setup exactly it seems like. I am a dummy when it comes to this stuff, as this is my first system ever.

1)Let's say I don't use my QSC for my gig this Saturday (which I won't). The way I have been hooking up my Fender to the speakers (which are two Fender 115-ELC's) is by going from AMP A (the quarter inch output jacks on the AMP itself not from the MIXER Main OUTS) to one speaker and from AMP B, to the other speaker. Or someteims I would just use only one AMP A or B and go to the two speakers (there are two quarter inch outputs for each AMP).

IS THIS THE RIGHT WAY TO DO IT? IS THIS THE BEST WAY TO DO IT?

(by the way its a wedding hall in a hotel, about 200 people).

2)Back to what you have explained above. My QSC USA400 Has two input channels on the back and right below them is a SWITCH that says BRIDGE MONO on one side and STEREO on the other side, so yes my QSC does allow bridging. Are you saying I go from my mixer MAIN L (lets say) into the OUTPUT of the Fender AMP below it????? OUTPUT TO OUTPUT? The Fender AMP does not have INPUTS...all its got is two AMP A outputs and two AMP B outputs, and it is connect to the mixer through some internal wires in the WOOD CASING! Can you please elaborate in more details on this point?
Also you said, you run the other channel to the other AMP...are you saying the other AMP as in the QSC , or the AMP B? Again if you can re-explain I would really appreciate it