Ended up picking up the Radium 400W single ended bulbs, from ReefGeek for $54 a piece duing his Black Friday sale.
Just make sure you get single ended bulbs. Your options for double ended 400 w are hamilton and catalogue. Made that mistake with my 300g
I've been looking, 'cuz I really thought that you were wrong, but I hate to admit, I can't find anything in 400 watt DE in the places I look for bulbs.
Ended up picking up the Radium 400W single ended bulbs, from ReefGeek for $54 a piece duing his Black Friday sale.
I have this bulb in my center reflector in my 300g. LOVE it! The color is awesome. The corals also love it. I think you're going to be very happy!