Well technically I don' t think that they were intended to be transferable. If you encounter a ticket agent or lounge attendant that asks to see your "Guest Rewards Select" card you could have a problem.
However I've never had anyone ask me for my card and I don't think that Amtrak really cares if someone gives them away. I've given out a few to one of my friends. On the other hand, Amtrak might take issue with someone selling them if they get wind of that auction.
As for using them on the west coast, the lounge coupons won't help you much at all. They are not good for Metropolitan lounges, only Club Acela's. The free upgrades though, you can take advantage of.
One can either upgrade to first class on the Acela's & Metroliners or they can upgrade to business class on any other train. There may be one exception to that BC upgrade, it may not work for the Palmetto. So if you got one of those coupons you could still use it on the Cascades service.