Take the XLR out or the TRS from Sansamp into the QSC. Then the Speakon into the Left input of the Ampeg Speakon.
Set gain on Sansamp to desired level. Set Output of Sansamp to start at 1/2 and use QSC formain volume into Ampeg.
You may need to do some experimenting with Output of Sansamp opposed to QSC just for volume purposes. You might need to turn the Sansamp up so you arn't cranking QSC or the opposite.
Hope this helps...
"Let us not become weary in doing good, for at the proper time we will reap a harvest if we do not give up."