Has anyone tried Lyn? It's a basic image browser/viewer for Mac. It recognises Sigma X3F files, will display EXIF info and you can view the image with it and zoom to 100%. It clearly uses the embedded JPEG and isn't processing the RAW but it is an incredibly quick way to scan a card full of images. From within it you can delete any duff ones, open the file in SPP (or other app) for further processing and even publish to Flickr etc.

Oh, also a slideshow facility, again using the JPEGs but a really quick way of previewing a session of photos.

There is a trial version but the full only costs 16GBP.

Lyn - Lightweight image browser and viewer designed for Photographers, Graphic Artists and Web Designers

Worth a look, I think.