I don't know if your question was asking about a DIY LED setup or a kit.
I couldn't find the price of the JBJ LED, but if you purchase it from nanotuners it will be $260 i think for the cheapest CF tank and then about $400-$550 for the LED kit. I don't know if you are trying to go SPS/Clams or something else, but for SPS/clams I would recommend the higher range it has all the upgraded emitters, drivers, and fans. However it will not be dimmable unless you hook it into a Reef Keeper Lite or Elite and ALC module or other type of controller system. The dimming is good because you can tweak the lights to any look you want the tank to have and also simulate sunrise/sunset. I'm pretty sure Nanotuners will install the kit for free and shipping will be free. Keep in mind there will be a waiting period depending on how busy they are.
If the dimmable function is not necessary you can acclimate with screens and will be less money, but I just got the kit in my biocube a few weeks ago and when you turn off the whites to check out the actinic look my fish all start freaking out. Clowns start fighting, Royal Gramma starts attacking clowns and other just hide. Its really weird, it never happens other then when its just the actinics on. I think it is just the sudden extreme change that wasnt as extreme when I had the stock CF lighting.
If you are leaning towards the the Nanocube LED aquarium, I recommend finding information about the LEDs, emmiters, heat sink, drivers, etc. that are installed in there and maybe posting some questions on here or Nano-reefs.com to make sure they will be ideal for what you are trying to accomplish with the tank.
Hope my blabbering contained some helpful information haha