My undergraduate degree is from Auburn and my masters is from Indiana University. Basketball is huge at IU. So is greek life. However, it is well over 20,000 (over 40,000 total, and over 30,000 undergrads). On the other hand IU actually feels smaller than Auburn. So, I suggest keeping it on your list. The biggest difference between Auburn and IU is that the students at IU are considerably more liberal than those at Auburn (mainly because Auburn students are so conservative, not because IU is so liberal). Some people who live in Indiana will tell you that the liberals go to IU, and the conservatives go to Purdue. There appears to be some truth to this, but personally I don’t think it is a big deal.
Miami of Ohio might very well be the northern school which is most like a southern school. Definitely on the preppy and conservative side. Greek life is huge, but sports less so.
Ohio University in Athens reminds me a lot of Auburn – at least in the appearance of the campus (except OU is kind of hilly). It is almost exactly the same size as Auburn, with slightly more students.