For destruction, which I don't think is needed personally since wiping it will be good enough unless the government is after you and doing the DOD multiple pass (which dban might do) will take care of that). A magnet is not good enough to wipe everything in paranoid mode.
In a past life, the way the disks were destroyed was to remove the platterers, sandblast the magnetic coating, cut up the platters and then melt them all. Just removing the coating is not good enough in the worst case.
Using the multiple pass erasing is good enough for the DOD for secret projects. For what you have said dban is good enough at a llow level (it has been a while, so I am not sure if it has the higher levels of wiping, but I think it does). You can also fill the disk with random data several times.