The standard instal of 'Texture Resizer' on a mac uses sips, so it doesn't even call ImageMagick...
and it can use Goldilocks automatically...
if you had posted on that thread, others who have posted there will get emails and may be able to help...
post there and see who responds...
AS for editing materials from within SU, I and others have made a few post of how to get that working again...
john