At some point many hobby guys will likely aquire all of the above. I couldn't imagine not having a dry cut saw ( or 2 ) a few angle grinders with various wheels, Plasma and Oxy-fuel, Band saw, shear and nibbler. Enjoy.
I'm the same way.... Welding is a major hobby of mine, and that means cutting metal. So I've ended up with lots of tools - like various grinders, horizontal bandsaw, power hacksaw, lathe, mill, nibbler, post drill, drill press, and half a dozen more. There's even a vertical jig saw in the mix. All for MIG, TIG, ARC, but oxy-acet torch welding is still my favorite.
If I had to have just one metal-cutting tool in the shop it would be a medium size vertical bandsaw on a stand. Actually it wouldn't necessarily be medium sized... I'd would be as heavy-duty of a vertical bandsaw as I could find and afford - but medium size would do it. Even in medium size it would probably have to be a used one as new ones are real expensive & this is one of the areas where used is just as good if you don't mind doing basic maintenance & adjustment.
With a bandsaw you can cut out odd shapes close either close enough to weld them and even trim them to fit. A medium size bandsaw is slow at cutting thicker metal, but it will cut up to about 1/4 to 3/8" thick fast enough for most projects....how thick & fast depends on the bandsaw. A bandsaw will also do some nice woodwork, and it's a sort of friendly tool.... not a frantic tool....
And if you just spend some time getting to know how to use it, your oxy-acet cutting torch will do a great job of cutting everything from sheet metal up to half inch plate and leaves a smooth bright shiny edge you can weld too without anything more than knocking some slag off.
rScotty