Don't know much about water in TN, but some people can do it without RO if the tap water is very good. But the lucky ones are few, and I don't think TN is as well-known as the Pacific NW for water quality.
Anyway, check with your local water company for a water report, and see if it is good enough. PUR filter does not remove mineral, and may not do much to chloramine, so it can be an issue. I suggest you take a look at some fo the recent articles on water quality in either AAOM or RK online magazine and see if they can be of help to you.