Justin,
welcome.
so far, my cost Round Trip (R/T) from Portland (PDX) to Amsterdam (AMS) has been around 1200~1300 with 1300 USD for this year. I haven purchased my tickets yet, but the way things look, its going to be about 1300 r/t PDX to AMS. it will go up since i plan on adding some additional legs to the r/t this time.
by the way (btw) i use AMS as my hub since they have direct flights from PDX to AMS and i choose to fly non stop for now. just an for your information (fyi), i did take a cheaper flight on my first time with 2 layovers but it added 6 hours to my fly time. I saved 200 USD, but it cost me 6 addtional hours in airport. So you can determine for yourself its worth it.
Also, when it comes to $$$, dont be afraid to state your budget. different people have different budget and what they think of as "cheap".
Charlie may chime in. I believe he flys in/out of SEA.
IF you dont mind the drive to the other airport, then i would look at whatever less expensive flights that can be purchased. the cost of the tickets will be the deciding factor. Also, if you do use the other airport, add the cost of $$ and time of the drive to that too.
i hate driving so driving to SEA for a flight doenst appeal to me, however the greedy part of me could cause me to look if i can trim mucho $$$ off a ticket. but i doubt that will happen.
happy trails.