Ah, more information.
Easy, cheap fix, but takes a lot of work... face the tool boxes to the wall each time you leave, and have a simple steel bar to lock the boxes in place. I could sketch something, but it's hard to describe in just words. Think box faced in, bar coming from wall, another bar coming from wall on the other side, a cross bar holding the boxes in place, with a humongous lock.
The cage idea does work, and would be fairly cheap with wrought iron as well as look nice. And the cage isn't for you to drag your tool boxes in and out, as much as it is a 'tool room'. Make it big enough you can open the drawers inside and then you can keep welders, other big ticket items in there at night.
Or check your local zoning and put wrought iron over the windows (usual theft point) the man door, etc.
You can reinforce rollup doors nicely, or replace them with retail grade rollups, like you see in industrial parks.
Other thoughts;
On the motion detector, a siren is better than a stereo or something, flashing lights on the outside wired to the inside motion detector also work good, but be careful you don't get a noise ticket if you have a false alert.
Decoy system;
Strongly secure your good tools, don't use a lot of effort to decoy some shiny but cheap tools.
You can assume most thieves will not be driving up with a huge large lorry (sorry, truck) and having six friends to help steal.
Most will be kids or bums (what we call homeless) or druggies, who will be carrying the stuff. If their hands are full of cheap junk, that they got easily, they may not move on to the good stuff.
We used to let the thieves steal stereo boxes with bricks in them, or defective stereos. Lost a lot of junk and bricks over the years...those guys never seemed to come back.
