I'm not sure where you are based. KLM worked for me out of YYZ. Their gold status gives you access to DL lounges for free when traveling in the US with DL. KLM is pretty good about offering op-ups to AMS from YYZ for their gold and platinum members. I received upgrades to both J (off-season when the loads are lower) and their premium economy (more leg room) in the summer. You do have to watch your fares in the US with DL as often you will only get 25% of your points.