Never thought I would disagree with the gardening-guru, Baccy Man - but 'Ludvig Dazzler' is pure white: I think Amazin's one, with its fine, red edging, could be 'Picotee'?
(http://img518.imageshack.us/img518/2557/9570hippeastrumfl7.jpg) (http://imageshack.us)
(http://img518.imageshack.us/img518/2557/9570hippeastrumfl7.c52e8c2203.jpg) (http://g.imageshack.us/g.php?h=518&i=9570hippeastrumfl7.jpg)
But I'm not sure!