I'm convinced that your choice of K ratings for bulbs is just a personal preference issue. In fact I asked some time ago if anyone had ever tested actinic bulbs to see if they really were of no value to the plants, and no one had. So, use whatever bulbs makes the tank look as you want it to look. I'm not clear yet on what the life limit on PC bulbs is. I used my 55 watt bulbs for about 15 months, and they didn't seem to be any different at the end - but I admit when I replaced them with 36 watt bulbs I couldn't see much difference.