I'm not the guy to ask. There doesn't seem to be a single opinion on whether to under-power your led or use the rated wattage. The setup I'm using is slightly under driven which theoretically should extend the life of the chips. If I were to guess, I'd say you would need a bigger driver.
For...
Using the basic parts outlined in the first page of this post, I built a scaled down version of this light with some changes.
I mounted the leds to the heat sinks and stuffed them inside 3" pvc and use a blower to cool all 4 lights. The output of the blower is vented outside via some 2 1/2"...