When you want the best plant, it’s great to have a local expert. Lyndy Broder is an internationally known clematis expert in Georgia. She recommends the following:

C. ‘Arabella’ (integrifolia) blue-mauve, blooms April-Sept., use trailing on the ground
C. ‘Betty Corning’ (viticella) pale blue, blooms May-August, climber 8-10’
C. ‘Duchess of Albany’ (texensis) bright pink, blooms April-Oct., climber 8-10’
C. ‘Etoile Violette’ (viticella) dark purple, blooms April-Oct., climber 10-13’
C. ‘Henryi’ (early large) white, dark anthers, blooms April-July, climber 10-12’
C. ‘Josephine’ (early large) double pink, blooms April-Sept., climber 8-10’
C. ‘Madame Julia Correvon’ (viticella) red wine, blooms April-Sept., climber 8’
C. ‘Princess Diana’ (texensis) luminous pink, blooms May-Sept., climber 6-8’
C. ‘Rooguchi’ (viticella) purple blooms April-Sept, 3’
C. ‘Venosa Violacea’ (viticella) white with purple veining, blooms
May-Oct., climber 8-10’

Sources:
Joy Creek Nursery (Oregon)
Brushwood Nursery (Georgia)
Woodlanders (South Carolina) for native clematis