Sorry, but Qwest and Clearwire both cover nearly all of Seattle as well. You can argue about how broad you have to be to be called broadband, but they are both going to be suitable for a home user.
I have Qwest because Comcast can't provide reliable service to my 1920s apartment building, and I only get 2.6 Mbps down. I wouldn't think I'd have to explain on HN why that's not a viable alternative. It's certainly not for the OP's use case of streaming video.