I've recently integrated a Digitech RP-6 multi effects into my rig for delays, chorus etc... and it doubles up as a backup straight into the desk in a worst-case scenario. I do have a Boogie Studio Preamp which sounds great into the desk, but its not yet in our rack. Once it is, that will be my main backup. Our set-up is quite full on though with racks of gear, a 4k RCF rig (tops and subs), A&H G3 desk, rack with compressors/gates, EQ, reverbs, stage-boxes/looms plus monitors.