"Today marks another milestone" for Atlanta, Mayor Kasim Reed said Wednesday as he announced that the city had entered into an agreement to sell Underground Atlanta to WRS Inc., a real estate investment company based in South Carolina. WRS will pay the city $25.75 million for 12 acres of downtown real estate, which the city will use to pay off the remaining debt on the property. It also will cover the costs of buying out the 70-year sublease that existed on the property - a deal the city completed…