Powell made seven three-pointers while Jaime Jaquez scored 19 points off the bench, Andrew Wiggins added 17 points, and Bam Adebayo contributed 15 points and 14 rebounds as the Heat improved to 19-15.
The Pistons suffered their third loss in four games in falling to 25-9, still the second-best record in the NBA behind Western Conference leader Oklahoma City (29-5).
Cade Cunningham powered the Pistons with 31 points, 11 assists, and eight rebounds.
Also stretching their win streak to four games were the Houston Rockets, who got a strong performance from Kevin Durant in a 120-96 victory at Brooklyn.
Durant scored 22 points and made a season-high 11 assists while Amen Thompson added 23 points on 10-of-12 shooting in sparking the Rockets.
Houston (21-10) also got 20 points, six rebounds and six assists from Alperen Sengun while the Nets (10-21) were led by 21 points off the bench from Cam Thomas.
At Dallas, Tyrese Maxey struck for 34 points, 10 assists, and eight rebounds to lead the Philadelphia 76ers over the host Mavericks 123-108.
The Sixers had 23 points from V.J. Edgecombe, 22 from Joel Embiid and 19 points, seven rebounds and three blocks from reserve Quentin Grimes off 7-of-9 shooting.
"Needed to come in and just try to be myself, be aggressive, be in attack mode, try to get myself and my teammates involved," Grimes said.
The Sixers improved to 18-14, fifth in the Eastern Conference while the Mavericks, led by 18 points from Max Christie, lost their fourth in a row, falling to 12-23.
Grimes likes the Sixers' chances of being one of the top East contenders come playoff time with Embiid back from injury and Paul George playing like his top days with the Los Angeles Clippers.
"We're getting Joel back to full speed and Paul is getting back to where he was when he was with the Clippers," said Grimes. "So as long was we take it day by day and keep getting in rhythm with each other... I feel like we can be one of the better teams coming out of the East absolutely."