As for the modules, I have the same fixture, and I found more tanks that were successful with the multicolor LEDs than just white/blue. I initially chose to go with three modules, but then bought another three when I thought it wasn't cutting it. I have a center brace, so that middle slot would be marginally effective anyway.
I personally think that the tank is a bit white (I run at 100% B/RB and like 70-80% white for a good part of the day). It probably is a little less than 10000K during the peak of the day. I have been considering adding a couple of stunner strips to add some more blue - I was hoping to be 14000k or so.
BUT, and this is a big BUT, I find that the tank grows corals really well, and I've scheduled the whitish period so that I'm not usually around for it. The sunrise/set times are much more blue/violet. So, while for looks I probably would have gone three multicolor and three blue modules, I think growth and color are probably better under the six multicolors.
I'm not sure if I made your decision easier or harder, but that's what I've found.