KSU has been better than Iowa and more difficult for ISU to beat than Iowa. Also finishing higher in conference standings is a bigger deal than a non-conference game in September.
The biggest wins over the last few years have been OSU, TCU, Texas, and Baylor in 2012 so it's time to add a win vs. someone a bit more familiar.
KSU for obvious reason, but I'm sure we'll end up losing by a point or 2 after leading for 3/4 of game. OU would be next, just because of how good they're supposed to be and we're something like 2-349 against them.