Eddie,
I live in Lexington, SC too. I have been renovating an old house for the last few years and using existing stock when I needed some hardwood so I haven't bought any. But there used to be a guy selling out of tent buildings south of the airport area that was not bad. He planes everything and sorts out figured material he charges more for. But prices are decent, nothing like Mann. I agree with you about them. It's nice we have something in town but their wood inventory is tiny and their prices are not. I'm not sure if he is still around. He was only open half days in the morning during the week last time I bought from him.
I've driven up into NC several times for wood. I've never been disappointed. I have a lunchbox planner and small jointer and buy rough when I can.
I have difficulty getting 3/4 or 13/16 from most rough sawn wood too, however, if I flatten one face first. Some of my issue is technique but some is the boards. I often just plane it to the needed thickness and deal with the fact it isn't totally flat. Sometimes I flatten it and when I then plane the other side it shifts too. It's frustrating at times but I blame it on the quality of the wood. Could be at least as much me. Dealing with lack of absolute flatness and straightness is part of woodworking in my shop.
Jim