Here are five albums from Basie's New Testament band. All of them are stone-cold classics. IMO, you really can't go wrong with any of these:
One important thing to consider when you're digging into New Testament Basie: Who's the arranger? You mentioned the Atomic Basie record. That's Neal Hefti, one of many arrangers who wrote charts for Basie in the 50s and thereafter. Each arranger that Basie hired brought a little something different to the table -- even if all of them work within Basie's overall sound. Frank Foster's arrangements have their own touches that are quite different than Hefti's. Same with Ernie Wilkins, Benny Carter, Quincy Jones, Sammy Nestico, Chico O'Farrill, Bill Holman, and so on.
For my money, the most interesting NT Basie arrangers are Frank Foster and Benny Carter.