Hey Rich G.-
If you don't have a keyboard player, there are some four and five part doubling programs on our harmonizer...a Digitech Vocalist VR. If you're interested, I'll run through them next gig...tomorrow night. If they work, you won't have to MIDI it to anything...just bring up the program.
For stadium-sized shouts, I'm pretty sure this is the effect you're looking for. It works for us. It's huge, always reliable, and doesn't require fine-tune tweaking. I guess it's a matter of...do you want to spend $300 to get the sound?