Filter 1: Is a Highspeed Project feasible?
A highspeed track should be used for transporting as much traffic into the whole area as possible. Before it can do that, it needs a core business, though. Just speeding up things does not help - there needs to be a city pair in 1.5 - 3.5 hours highspeed travel time distance, that generates huge amounts of traffic, and is the main justification for the huge expense of an all-new ROW.
When discussing high-speed rail, the first look has to go to maps of population density and population distribution therefore.
It is no technical problem, to travel to Eugene within favourable time, with a highspeed line from Sacramento. But between Redding and Eugene, building a ROW is utterly expensive for topographical reasons, and Eugene is too small, to act as a major feed for a high-speed line. Both Portland and Seattle would have to be reached with a timetable, that is competitive to air, in order to make true high-speed feasible.
Conclusion: Distance of population centers is too high for a true high-speed rail project. If there is a useful function for passenger rail in this corridor, it will be found in serving a much smaller market at much lower investment.