The best place to watch a Sounders match is, obviously, at Qwest Field, with its marching band and giant-sized glitter that rains down on the Astroturf. (Is that not distracting to the players? Maybe they'd be scoring more if they played sans constant dazzlement?) But even the $20 cheap seats plus stadium-priced beer and snacks is a fast wallet-emptier.
If you want to experience the joy of victory, the agony of defeat, or the seeming inevitability of a tie en masse without mass expenditure (or for away games), the George & Dragon Pub (206 N 36th St, 545-6864) in Fremont provides the highest quotient of Sounders-regalia-wearers. Everyone's a fanatic, making for extremely satisfying mass reactions—the entire crowd responds as one lime-green-and-blue organism, fueled by pints and decent fish 'n' chips. In 2006, the George was voted one of the top 10 places to watch un-American football in the United States by GQ. If (hope springs eternal) the new home team goes anywhere playoffs-wise, this will be where the party is. Bonus: a good-sized deck with TVs, too.
Across the street and down a block is Seattle's newest soccer bar, Azzurri Vino Bar (223 N 36th St, 547-1050). As detailed recently here, it's kind of grubby, but Italian owner/proprietor Michele Zacco is awesome; he broadcasts occasional decisive commentary while handing out Peroni and pouring wine. Where the George is a reproduction of a dark British pub, Azzurri's a low-key, thrown-together neighborhood place. Bonus/warning: Children may be present.
On Capitol Hill, Cafe Presse (1117 12th Ave, 709-7674) is entirely civilized; if you want a perfect omelet and a Lillet with your soccer, this is the place. Some people are glued to the game; some have one eyeball on it while reading the newspaper with the other. The Summit Public House (601 Summit Ave E, 324-7611) is like a pleasant cave that happens to have several TVs and 22 beers on tap. Food: chips (or pizza from next door). Then there's the Elite (1520 E Olive Wy, 860-0999), an airy, wholesome gay bar where everyone's welcome and discussion is bound to turn to jock straps and the contents thereof. Bonus: good drink specials to go with the good one-liners.
In the Seattle classic department: the Roanoke (2409 10th Ave E, 324-5882), where local soccer teams have gone to drink after games since the beginning of time, is another Sounders headquarters, with the benefit of quite above-average pub food. Also: ping-pong on the back deck for halftime. And in the destined-to-be-a-classic category: Ballard's the Dray (708 NW 65th St, 453-4527), which is all toasty-colored wood, with pretty great sandwiches and a mighty impressive beer selection. Soccer or no, you should go. 
