Memphis would be a nightmare. CSU is just a better fit and if the Big12 wants to go to 14, and they have to invest in a university, CSU has all the upside and very little down.
New Stadium
Out fundraising everyone but BYU (Cincy has a med school, so they don't count)
Football recruiting out of SEC country (thank you Univ. of Georgia OC BoBo)
Basketball will be top 40 this year and make NCAAs
Solid Research School
Big TV Market (vs. Memphis? Please!)
Land Grant University
Easy access via airport
CSU is not where BYU is, but is not far behind either. They can own the Denver market with a little help.