If you are cutting stainless with a metal variable speed band saw, the best way is to friction cut. Turn the blade speed way up, 3000 fpm and have at it. Don't start with a new blade as this speed will ruin all of the teeth but the speed is so high that the friction of the blade against the stainless will cut the tube. You can actually put the blade in backwards and it will still work. I would think that this type of cutting might work with a steel blade in a high speed cut off saw but have never tried it.
Regarding the purging there is also a special flux that you can use for welding stainless that will give pretty much the same result as purging and of course for the life of me I cannot think of its name!! CRS!!!! I am sure someone on the site will help me out here.
Rex