I have removed lots of stuck stem and seatposts and before you enter the destructive methods try liquid wrench. no other penetrating oil or what have you works as well. If you have time let it sit upside down with for a weak. Give it a could whacks every day. I like to hold the handlebars and put a good hickory shovel or something between the fork blades at the crown. two people can twist opposite ways. If you haven't tried liquid wrench... you haven't exhausted your options.
1 Super Record bike, 1 Nuovo Record bike, 1 Pista, 1 Road, 1 Cyclocross/Allrounder, 1 MTB, 1 Touring, 1 Fixed gear