I"ve been doing a lot of research on this aswell, i've seen a few nice tanks with 40 degree optics, some even with 20. They tend to be layed out in a cookie sheet way, staggerings each line of LED's. I think it's more dependant on your density of LED's and the height mounted oabove the tank. 10" above the tank is pertty common, If you are going more than 2.5" centers on the LED's i would suggest 60 degree, if less than 2.5" then 40 should be fine IMO. Check out as many pics as you can to see what you're getting into.
and if you are using XP-E's a 1:1 ratio will be a 14K balance, if you use XP-G white's you can get away with less whites, forget the combo for 14K though. The blue's don't help growth much, basically for our viewing and popping coral color (The datasheet for cree shows this with the light off the whites, it's very close to the PAR we're looking for)
As for heatsinks, there's lots of choices, but generally people WAY over build heatsinks. Cree's give off a lot of heat, no doubt, but you can calculate the heat gain vs loss pretty easy to see what you actually need.(i posted links on some other recent DIY thread)
Drivers have lots of choices, meanwell's are popular as with the buckpucks. More drivers gives you more "zones" for dimming/control. 1 driver dims all the lights together.
As for cheap controllers. Depends on how fancy you want to get... but look at arduino boards. There's LOTS and i mean LOTS of LED builds using these. Uses C programming, but i've found many chucks of code online that people have posted that got their LED's working and controlable. Arduino's start at $20 for something that will control 2 drivers with PWM outputs and $35 for something that'll do 6(Arduino Mega). If you get into it the arduino can do pretty much everything, i'm building a tank controller based off one right now.
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