If UNC and Duke are not tied together then I could arguments for adding NC State and Louisville as teams 5 and 6 if they chose to go that far. If they are tied together and the conference opts to only add 4 then I could NC State being #4.
The only 3 that I view as ones the B12 needs to go all-in for if they're options, though, are FSU, Clemson, and Miami. Anyone else would be secondary to adding those 3.