Skylsdale, the thing you are forgetting is that the water column absorbs a large amount of light, mostly of the longer wavelengths (red). *That's why deepwater corals use more actinics (blue, high K) than shallow reef corals. *Continuing the progression, a terrestrial plant will actually see a lower K color temperature than the reef corals. *FW tanks are also commonly lit with lower K bulbs than a reefkeeper might use, because the plants often grow barely submerged at all.
I have to disagree with some of the statements in the original post, too. *My CPs are currently under 3500K lights because that's all HD had when i bought them, and i haven't bothered to pick up others yet. *The plants are growing well. *I have noticed that some seem to feel "underlit" while others are growing and coloring nicely, which just seems to strengthen the suspicions i have that actual PAR spectrum and useable light is very plant dependent.
One thing that was left out so far is that there are essentially two types of linear fluorescents commonly in use: the old T12 and the preferred (efficient) replacement, the T8. *This is quite important to people setting up new grow areas, because the market and availability is changing (relatively) rapidly right now, and some vastly superior options may be missed if this isn't understood when buying. I've already written a volume about this (LOL) based on my rather extensive online research to the listserv, but if anybody missed it and wants to read, i put it up as the beginning of a FAQ a la Krib here. *Which reminds me, the Krib, one of the first and best aquarium hobbiest web sites, has a lot of information on lighting.