Just remember, when flying to SEA you'll still be a very long flight from Seoul, Tokyo, etc. There are some rumors that EVA airlines is going to expand on the east coast soon (I think I heard IAD). If you don't mind waiting for that announcement you might be able to snag a PE or J seat on the cheap. From Taiwan, it won't be an awfully long flight. If Hong Kong flights come back it could be a good option too, and just try to get on a star alliance airline or local one on the cheap.