What does Premium Aquatics say?
FWIW, I had to return an XM bulb to them recently. It just died after a months use. They said they had lots of problems with the bulbs. (Mine was 175w, not sure about the other wattages).
They also come highly recommended by myself.
You can get most everything from them that you can't get in Canada and they will send it via post, unlike Marine Depot.