Take a look at pdga.com and look at the past big events in the area (First Class Challenge, Legion of Doom, River Cities Rumble, Minnesota Majestic), and you'll have a real good idea of who would be interested.
If you have a sponsor, my suggeestion would be that you hook up with the tournament director of one of the events I listed above and work with them to make one of those events bigger and better, rather than watering down the market farther than it's already been (i.e. adding another tournament). There's too many events IMO, but plenty of events that need better/more sponsorship. You could also look through other Iowa events, and pick one that could be made bigger. (My suggestion for that alternative would be the Des Moines Open or Iowa State Championships.)