I'll do a little digging on the ratios.
I've written down in my notes that 1rb:1cw = 10000-12000k ( I haven't noted where I got that info from).
the addition of the extra cool whites (5000-8300k) should soften the effect. can anyone confirm if I've got this right?
I'll have a look at the cheap LEDs. from my understanding the crees put out more light using less energy ( thus meaning less driving power for each string or more LEDs)
as well as what you mentioned with the accurate wavelength peaks. if the led peaks at the wrong wavelength then it potentially could be useless to plants become purely mood lighting ( eg red (670nm) and far red (730nm which is outside PAR).
This company http://buildmyled.com/custom-led-strip/
has a diy app that would take a lot of the guess work out in figuring which leds to use. Using this app I've created a light with a K temp of about 5700-6000 and a color rendering index of 98