I realized we have a sous vide in our kitchen. Bought it a few years back, but somehow we forgot about it. Now you have made me dig it out again, and I want to test it on a filet steak (medium rare). My question was, sear it before or after? I'll try the "after" first.

I'm not too much worried about the plastic. I'll use my vacuum-packing device to seal it. That should work.