not true at all K ratings are over rated and if your using cfls you should know by know that 5000k puts off more red than bulbs rated around 3000k.
although it is true that 3000k appears more red than 5000k it is actually more yellow (that the 5000k doesn't have replaces with blue phosphers) and red.
5000k rated cfls put off more PAR light than 3000k.
okay now back to hps. you should bever base your bulb purchase on a specific K rating ratings will vary between 2700k and 3000k. most brands are good but some are better than other(putting off more red light or splash of blue spectrum ect.)
so very well made HPS bulb brands are, Hortilux(splash of blue), digilux(reddest looking HPS out, digital ballast only) and Phillips(quality).
now each bulbs is going to differ slightly from the last so there is no guarantee you are getting the spectrum they advertise, all you can do pick the best brands. send the cash where it counts. i guarantee a sylvania hps will preform, but i seriously doubt it would out preform a phillips lucalux? as far as both spectrum, luminosity, and durability.
