Hmm 460-470nm blue, wait a minute.... Peak absorption occurs at 425-445nm around 99% usable light where as 460-470 is around 85% usable light. And as you said low amount of lumens which means you need to maximize the potential of absorption from your LEDs so why settle for 85% when you can use nearly ALL the light an LED emits by getting the proper wavelength. Please don't tell me I don't know what I am talking about, I have several charts of the absorption spectrum of cannabis in front of me and I visited your link. I am not trying to be an asshole but don't tell me I gave mis-information when I didn't.

Want a perfect LED grow light? 65% blue and 35% red for veg, reverse it for bloom but start bloom with 100% red for a few weeks.
425-445 or 450nm for blue and 640-660nm for red.
Using clones? 90% blue and 10% red when rooting. Any questions? Ask and I will try to answer them.

Now that is the cheap version. To get the best absorption you have to match the absorption spectrum perfectly, the sun doesn't even do that but it provides so much light it doesn't need to. Your LED grow light won't so you need to match it within 10% I would say to maximize the investment to payoff. This means you would need some green, purple, yellow, orange. Hell you would need every wavelength LED to cover from nearly 400-670nm and that would require a shit load of moolah, which most people don't want to spend so I will spare you all the exact details b/c I would get carried away.