The pinned lighting article should help but here's some more info that may help.
K isn't as important as quantity of light. With enough light, plants are unfussy.
In a low light set up then spectrum becomes more important as the plants cannot rely on quantity of light. In a high-tech set up then choose what suits your taste and budget and the quantity will be sufficient to grow plants.
I prefer around 6500K as these render the greens very nicely.
Less than 6500K = more red. More than 6500K = more blue.
Plants need red and blue parts of the spectrum to grow. Most full-spectrum (with 3 or four peaks) lamps produce peaks in the red, green and blue so are ideal for both plant growth and viewing.
Generally speaking green plants do better with more red, red plants with more blue light.
Many of the "old-fashoined" plant growth tubes i.e. Gro-Lux and Arcadia Original Tropical have good red and blue output but little green. This makes them good for growth but poor for aesthetics (IMO).
Combining tubes is effective as the many parts of the spectrum will be produced making the colour rendition effective as well as plant growth.
FYI I've grown plants successfully with 3000K up to a claimed 18000K.
Actinic and very high blue spectrum tubes desgined for reef may encourage algae growth.
