Whew, that's a lot more than I had figured!
I have seen Cedarburg, West Bend, and Germantown's bands perform, but knew of only a handful that competed: Lutheran Vanguard (Appleton), Lighthouse Brigade (Milw?), Shadow Armada (Oregon?), Waukesha, and Sun Prairie. Madison Scout's Whitewater Classic had some of them perform prior to the DCI competition.
I have performed at Lambeau with the Americanos (early-mid 70s, was really quite thrilling!), and I'd certainly love to see Green Bay's revamped stadium host a show. The region could easily accommodate the corps.
edit: oops, forgot West Bend...