Glad to have you here in SC. You'll love it, don't know if you'll love have your equipment in the garage though unless your door is sealed somehow and it's air conditioned. It's going to get really humid in there, as you know!!
I think 24" is as much as i'd go for your height, it gives plenty of aquascaping options and allows reach to the tank bottom with, any more and you have to climb in, I wish I'd gone smaller than 24" in height and got more depth.
I take it you've been to Tideline? It's the only LFS worth your time and money on Charleston. And then of course visit Ultra Corals (reef king) for your frags.