The Boston Celtics are known for their big three, but it was an additional two who spoiled the debut of the 76ers' new president and general manager, Ed Stefanski, tonight.

While Kevin Garnett, Ray Allen and Paul Pierce were responsible for the buzz at the reenergized Wachovia Center, free-agent signees James Posey and Eddie House torched the Sixers in their 113-103 loss to the visiting Celtics.

Posey scored 17 points off the bench, hitting 4 of 6 shots from beyond the arc, while House added 15. The Celtics' bench outscored the Sixers reserves, 46-26.

The Sixers lost despite receiving the first double-double of the year from Andre Miller, who had 26 points and 12 assists.

"We had to give up something to defend the big three, and the other guys hurt us," Miller said. "Our rotation was decent, but they just hit their shots."

Stefanski will realize that his biggest task is fielding a team that can put together two decent halves.

For the third straight game, the Sixers couldn't match their effort of the first half in the final 24 minutes.

The Sixers played about as well offensively as they could in the first half and held just a 57-52 advantage after leading by as many as 11 points in the second quarter.

That wasn't a good omen.

"We need to realize defensively we have to come harder in the second and the fourth quarter," said Sixers center Samuel Dalembert, who had 13 points, nine rebounds, and six personal fouls.

The Sixers trailed by 83-80 entering the fourth quarter, when they were outscored by 30-23.

House had 10 points in the final period and Posey added seven, hitting two three-pointers. This season he has shot 20 for 38 from beyond the arc.

"We know that teams have to pick their poison when playing us," Posey said. "K.G. [Garnett] does a good job of getting the ball to the open man, and we were able to hit shots."

It's not as if the big three were invisible. Garnett had 22 points and seven rebounds. Pierce, who took only 11 shots, scored 19 points. Allen was off his game with 12 points, shooting 3 for 12.

Besides Miller, Andre Iguodala had 24 points (on 10-of-17 shooting) and Lou Williams came off the bench to score 18.

The Sixers (5-13) shot 55.7 percent from the field and still lost. The Celtics (15-2) shot 52.6 percent.

The difference in the teams, as the bench scoring showed, was the Celtics' depth.

"Boston has good players, a good basketball team, and I thought for 40 minutes, we were there," said Sixers coach Maurice Cheeks.

"They have a lot of players and spread the floor with a lot of shooters, and you pay the price."

Boston didn't play its best game, especially defensively. Against a team like the Celtics, the Sixers have to play out of their minds to keep pace.

"The Celtics are really good and they can play any offense," Iguodala said. "They have a Phoenix-type offense and pick-and-roll, and Eddie House hit a few shots."

Actually it was more than a few. House was 5 of 10 from the field, including 3 of 7 from beyond the arc.

"They have guys that can spread the floor, coming off the bench with Eddie House and James Posey, guys who can shoot the ball, who can shoot the three with the best of them," Cheeks said.

At least tonight, that proved to be the case.

Contact staff writer Marc Narducci at 856-779-3225 or mnarducci@phillynews.com.

Read his blog at http://go.philly.com/deepsixer.