You're welcome for the link for the rock. There are 4 pet stores in town, you've listed them all. Pet food center has fish stuff but does not have any LR or livestock for saltwater. L and L has stuff cheap, but cheap isn't necessarily best, I question the quality of their livestock. Pet Palace is a nice place, but you will pay for higher quality. I think their live rock is $8.99/lb, and they have some pretty good looking rock there.
Your only other choices for LFS are Emerald Bay or The Aquatic Critter in Nashville. That's all that I know of, but look in the local suppliers sticky on MTRC and you'll see either their sites or addresses.
Wish I could help on the RO/DI, but I'm still getting mine from Walmart.