Having lost the first leg 1-0, the Blues recorded a 3-1 win at Stamford Bridge to give themselves a 3-2 aggregate victory in the last 16 of the tournament.
"It was a great game and a great victory against a good team, so I think everybody here on our side will be pleased," Benitez told the club's official website.
"We knew Steaua are a good team and we knew they had some strengths and some weaknesses, so we tried to exploit the weaknesses but still we were a little bit worried about their strengths.
"We had confidence before the game and we have more confidence after the game because we came back against Man United with some character, passion, commitment and quality and today was exactly the same. We had all these things together against a good team."
Chelsea return to Premier League action on Sunday when they host London rivals West Ham United.