The 2-0 victory at Bristol City came courtesy of goals from Danny Haynes and Michael Morrisson, inflicting a seventh straight defeat on Derek McInnes' men.
"It was the complete performance as far as we were concerned," Powell said. "It's the first time this season we have been able to say that.
"The midweek victory over Cardiff gave us confidence and today we defended solidly when we had to, as well as causing problems going forward.
"My two central defenders were outstanding and my goalkeeper came for as many crosses as possible, which helped.
"City were desperate for the points themselves so I am thrilled we competed so well. It is a result and a performance to build on."