Wow!!!! That is a lot of $$$ for 500W of LED's.
I would do my own build. I have used these LED's on my Reef tanks with FANTASTIC results!
These come in a 180lm/W version. 196 of these with 60 degree optics runs $325.75 shipped. Pair those with this driver (you would actually need 3 of them).
3 of these would run $345 shipped.
Total cost = $670.75
Add the heatsinks, fans, other goodies, and you are still below $1000 with everything and you are getting closer to 105,840 lumens with dimming capabilities using PWM, 1-10V, or resistors.
This will be a killer amount of light for a planted tank, but it would be completely dimmable.