WA-03: Probably Monica Stonier? Dean Takko is unlikely to run, and all the other strong Democratic candidates in this area live in Aberdeen which is in WA-06.
WA-08: Mark Mullet or Pat Sullivan
How popular are Newhouse and McMorris Rodgers? Are they at all beatable?
Newhouse is a generic R with no notable features whatsoever, but his district is extremely Republican, there are pretty much zero elected Democrats in the district (Even the Mayor of Yakima is a Republican).
WA-05 arguably already has one of the best possible candidates in Ben Stuckart. Besides him I would point to State Rep. Marcus Ricelli.