20000k bulbs have a lot more blue, less "white" light, so I suppose they appear dimmer. But the fact is your corals will still benefit tremendously, especially the light loving ones. You could go for a Maxima with that for sure.
I know what you mean, I have some PC
bulbs and they overpower my LED
lighting, though when the PC
bulbs are off the LED
lights are visibly bright and make glitter lines.
If you wanted your tank just brighter, go for some 14 or 10k bulbs because there will be a lot more white light in their spectrum.