Jays Tint shop in Kirkland is good. I think it was around 250 to have the whole car tinted except front windshield. he uses good film, and same price for any %. I had 20% before, but removed it to put 35% on, because it was too hard to see at night.
Just keep in mind that there is a bit of a stock tint and you'll be a tad darker than the film suggests... but since you aren't staying within the legal limits anyways it's not gonna make a huge difference. I just know a few people with 35% have gotten nailed by nit picky cops