there will always be a heat issue. i have 2-400w mh's and 2-160w VHO's over my 125g. i have 5-3" fans and 3-5"fans and i still needed a chiller.
as far as to much light, why do you want more light? what do you have on their now? do the corals you have now seem to be growing fine?
depending on what you have, going to this much light may be overkill for the coral you currently have. all you may end up doing is feeding the electric company more money! are you planning on going to SPS or clams? if this is the case then that would be plenty of light. in either case you will prolly need to take several weeks to get the corals adjusted to that much light.
G~
