Obviously the B1G would be the very best option for ISU.... in fact it would be a gigantic step up from where we are even now. So that is the dream scenario right now, not even a question.
The next best option IMO, is to join the PAC 12. I know there are people out there that poo poo that idea, but the money isn't much of a drop from where we are now, and the schools/teams would be WAY, WAY better than anything the Big 12 could throw together. I don't know about any of you, but I'd be thrilled to see USC, Oregon, Washington, UCLA, and even Colorado playing in Jack Trice Stadium. That would be sweet.
And I surely wouldn't mind taking a road trip to Boulder now and then. And we'd still have several of the same Big 12 teams we've been playing against forever too. I don't see how the PAC is so terrible if we don't land in the B1G? It surely beats a revamped Big 12 with Cincy, Houston, etc.... which don't do anything for me. I'd rather play USC and Oregon in the Jack than Cincy or Houston.