i can tell you're on the right track as to what you're thinking. like i said though, 4000k isnt putting out just one color. its putting out different colors of different values and the color temperature i believe is an average value of what we, the humans, can actually see. So, you're bulb would appear white and not blue like a 6500K lamp. That we know. But does it put out the significant amount of blues that a 6500k would do?

http://www.plantlightinghydroponics.com/eye-400w-6500k-full-spectrum-horizontal-metal-halide-bulb-p-93.html 400w 6500k MH

HydroBuds. 400w 4000k MH

and keep in mind they aren't made by the same manufacturer, so different product different results. and to your question about the cfls... i still think the wattage/"lumen" ratio for the MH would be better but still completely unnecessary since you already have plenty of light for a few small plants. thats other than the sq. space factor is all i can offer.
redaaron Reviewed by redaaron on . Need some advice .... Anyone be able to help ?? Im currently using 8 CFLs for Veg , but i do have a 400Watt MH laying around , only problem is that the bulb i have for it is only 4000K color temp... but does push out 36,000 Lumens. My CFL's are 6500K , just wondering which would provide faster growth , the CFLs with the right color temp , or my MH that has a lower color temp but puts out alot more lumens. Some advice would be great, Thanks Rating: 5