River City Groove is a pretty good pick, actually, even if just for their name. Chamberlain has always had a really strong music program. It's a very artsy little community. Their show choir is usually pretty small - 20ish students - but they handle jazzy chords pretty readily. My sophomore year of high school they made finals here and got 5th. Groton was 6th - and Aberdeen didn't make finals.
Here's that blast from the past:
Mitchell Show Choir Classic 2003
Grand Champion: Sioux City, IA - Bishop Heelan HS "Harmonia Mundi" (BV, BC)
1st Runner-Up: Sioux Falls, SD - O'Gorman HS "Ovation!"
2nd Runner-Up: Emmetsburg, IA - Emmetsburg HS "Varsity" (BB)
3rd Runner-Up: Sioux City, IA - Bishop Heelan HS "Pinnacle"
4th Runner-Up: Chamberlain, SD - Chamberlain HS "River City Groove"
5th Runner-Up: Groton, SD - Groton HS "Prismatic Sensations"
GC. Grand Island Senior High "Ultimate Image"
1RU. Marshall "Tiger Drive"
2RU. Vermillion "Rhythm in Red"
3RU. Papillion LaVista "Free Spirit"
4RU. Groton "Prismatic Sensations"
5RU.Chamberlain "River City Groove"
I don't see anyone taking out GISH. I think they'll win and sweep. This competition is a set up for the best possible way to end their season. I think Marshall and Vermillion will be after that. Papillion LaVista could jump up into the mix though. I haven't seen Groton for a few years, but they were good for a small SD school when I saw them. And after that I have no idea so I picked the coolest name (not really, but River City Groove is pretty fun.)