The former Great Britain stand-off enjoyed his first win in his second game as Tigers coach as Rangi Chase inspired a nine-try show at the Magic Weekend in Manchester.
"I'm delighted," Powell said. "I thought we played some outstanding rugby league but I was more pleased with the way we defended. We conceded a few points but I thought the attitude, effort and commitment was top quality."
He added: "It's great to get a win. We needed a win to start believing in ourselves. There is something there we can grab hold of and build on."
Winger Kirk Dixon scored four tries but England half-back Chase produced his trademark bag of tricks to lead the Tigers to their best win of the season. Chase, whose long-term future at Castleford remains unclear, mesmerised the Wakefield defence with his deceptive handling and expert kicking game as he helped create five of their nine tries.
"As far as I'm aware, Rangi is a Castleford player and he will stay that way," Powell said. "You never know what's down the track but, at the moment, he's a significant part of the team. He's an outstanding player and comes up with pretty special things at times.
"But he's got a group of people who are working hard for him. I thought Jamie Ellis was very good and our forward pack, who have had a fair bit of stick over the last month or so, stood up today. There were some high quality performances and Kirk Dixon's was certainly one of them.
"He was excellent and we had a ram raider on the other side of the field in Justin Carney, a highly-talented player who is very difficult to handle."
Wakefield, who won 37-16 win at Wheldon Road in March, were desperately disappointing as they lost further ground in their pursuit of a play-off spot.
"From start to finish, we were embarrassed by what we turned out," Agar said. "You can't dress it up. We simply didn't compete. They beat us to the punch in every facet of the game."
- Sports & Recreation
- Rangi Chase