Face Detection + Cropping
FYI... STASM uses OpenCV's face detector (albeit very slightly modified for better image-boundary detections). If you really want a better face detector then I recommend hunting down detectors from the FDDB dataset challenge (most probably proprietary) or create your own custom detector to fit your needs.

If you still plan on going the route of verification via eyes, then OpenCV has a cascade for that, see http://docs.opencv.org/doc/tutorials/objdetect/cascade_classifier/cascade_classifier.html