All of the main Seattle stores are covered in the posts above. If you have the time, and want to see a few different lines, you can also travel to Tacoma (about 30 miles south) and visit Advanced Audio Systems. The store is owned and operated by Curtis Havens, who has been in the high-end audio business for a long time. The store is just off I-5, south of the 56th Street exit. Here's the link to AAS's site:
http://www.advancedaudiosys.com/
I would also second the recommendation for Experience Audio. Tim carries an excellent line of products, and is highly knowledgeable (particularly about analog front ends and tube gear). He also has a very respectable selection of new LP's for sale.