Just to clarify...
W (watt) is not a measurement of how bright a bulb is. It's a measurement of HEAT. A lower watt bulb DOES mean a bulb that produces less heat, which means less heat transfer to your aquarium, and less fire hazard. But again, this has nothing to do with bulb brightness.
Lumens (or foot candles/candella) is a measurement of how bright a bulb is. This is the number you want to verify for a display tank.
In terms of Kelvin (color temperature), Natural (unfiltered) halogens are 3300k, 4300k is pure white, and most closely resembles the color of natural sunlight. (hence newer car headlight bulbs (HID) being 4200-4500k stock.) Metal Halide bulbs are in the 5000k zone, and is where the spectrum begins to have a blue tint to it. (some refer to this as ultra-white) 6000k has a light blue tint (some call this cool-blue), and as the numbers increase the color progressively gets more blue into the purples around 8000k.
Other people may have the same bulb design, but they purchased the bulb in a different kelvin, so it's better to not ask opinions about a bulb based on the name of the bulb alone.
The kelvin is also important (from the research I've been doing) for determining algae growth. A bulb in the yellow/red spectrum (3300k) will offer more algae growth, whereas a pure white or blue tinted bulb is more effective for your corals and for display purposes.
If your particular bulb really is in the 6000k range, I don't see why it wouldn't be suitable for display tank. Again, add up the total lumens (brightness) of your bulbs against the depth of the water in your aquarium to determine if you're overlighting, or underlighting your aquarium.
On a side note, I'm still trying to understand the photosynthesis process in SW
aquariums compared to FW
. I've had FW
for years, and it's common knowledge that red/orange/yellow/light green bulbs are much more important for plants/plant growth, but the blue-spectrum bulbs will cause an algae bloom very rapidly. I still don't understand why blue (though it looks much cooler, and apparently necessary spectrum for many corals) doesn't cause algae blooms in SW
Anyway, hope this helps you some.