M51 is part of the normal line. It has a decent movement in it as well. Not Swiss, but still good all the same. The lum on the lumbered watches are about as good as panerai watches, which is impressive considering the price difference. Some say its slightly weaker, but I think that might just be panerai guys claiming that to justify the money they spent on their Pam's.
I think if you get the watch you will likely be happy with it.