"It's a tremendous opportunity," Sounders goalkeeper Stefan Frei told reporters of the chance to repeat as champions against top-seeded Toronto. "We're going to give it our best shot to take advantage of it."
The second-seeded Sounders were barely pushed by the fourth-seeded Dynamo as Seattle managed to avoid conceding a goal for an MLS-record sixth straight post-season tie and extended their unbeaten home streak to 15 games.
Seattle's last home loss came at the hands of Toronto FC on May 1 but they will need to travel to Canada for the final due to their opponent's superior regular-season record.
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Victor Rodriguez opened the scoring for the Sounders at the mid-point of the first half when he lifted a deft chip over Houston keeper Joe Willis and Clint Dempsey doubled the lead in the 57th minute, tapping in a low cross from Joevin Jones.
Will Bruin completed the rout with another chip past an out-rushing Willis in the 73rd minute to send the 45,298 green-clad Seattle fans into a frenzy on a cool and clear evening.
Houston's main threat came from Tomas Martinez, who had two smart shots saved by Frei late in the first half before he was dismissed after the break for shoving Jordy Delem on the back of the head while the Seattle midfielder was lying on the ground.
The pair had made initial contact while jumping for a high ball and the red card came after a video review of the incident by the referee.
(Reporting by Rory Carroll; Editing by John O'Brien)
