This probably should be an "Off the Beaten Path" tip. Everyone visits the famous Loire chateaus but few venture off the beaten track to the other fascinating places nearby. Cinq Mars is between Tours and Angers. Along the road you will pass chateaus at Luynes, Cinq Mars, Villandry, Langeais, Usse and Saumur. Along the Loire tributaries are Chinon and Azay le Rideau. If you go east from Tours, there are Chenonceau, Amboise, and Chaumont all within an easy drive.
When you've seen Chambord, Chenonceau, Villandry, Usse and Chinon, try visiting some of the lesser known chateaus like Cinq Mars, Langeais and Luynes. They are all spectacular in their own way, not covered with tourists and often very friendly little places.