Getting ImageMagick to work by calling system() in PHP turned out to be more troublesome that originally assumed. Of course, Safe-Mode has be off, the dirs need to have the appropriate permission, and the absolute paths to 'convert' and your files should be set.

But still, it would not work. Despite executing directly in the shell quite nicely. The revelation came late, but better than never:

IM apparently hate single quote ' ', and absolutely insists on double quotes " " to wrap it's arguments in.

Can not really say, that this is well thought out... Anyways...