My welder and plasma cutter have lived under my bench for a long time, while the angle grinders and other welding stuff (extra wire, gloves, etc) all lived in boxes in storage cubbies. It worked out OK for welding at the bench, but wasn't very efficient in terms of storage space, and it was a huge PITA if I wanted to do any metalworking either on cars out in the driveway, or on larger projects in the middle of the garage. Then a friend send me a few pictures of nice self-contained metalworking carts, and I had to have one.
I started with a cheap harbor freight cart:
Cut the top down to fit under the bench, added hooks for cable management, hung a bottle caddy off one side, and put a heavy plate top on one side for a work surface. Looks pretty good so far...