And no, Texas can't get whoever they want obviously. Nick was infatuated with the Texas job, his wife loves Austin, and there was a lot more cash on the table than the ungodly salary. Mack was terrified about being replaced by Nick and was going to do whatever he could to keep that from happening.
Urban ain't leaving Ohio St. It, like Texas, is one of the top few jobs in the country and, more importantly, he's "home." He's an Ohio guy at his dream job and will never leave there to coach anywhere else, unless it's an NFL job and probably has no desire to do even that given his health history.
Peterson would be my top choice but he's not coming to Texas either. The reason he stayed at Boise for so long is because he has a kid with health issues and needs to be in that climate. He's not leaving the Northeast.