FirstBank, the largest Colorado-based bank with $27 billion in assets, is growing its presence in downtown Denver with the consolidation of operations and additional office space. The bank planned a grand opening Thursday at its location at 1144 15th St. FirstBank President Kevin Classen said the company opened a branch location on the street level a month ago and recently added office space on the Optiv building’s 20th floor. “This made sense to us because it’s a great way to centralize our team down there,” Classen said.