Bulbs, Brands, Types, Wattages, Color Rendition, K-Rating...
What it boils down to is PPFD and PAR.
If you want coral growth you'll need a high par reading. If you want algae growth go with a lower par reading. I don't care which bulb/ballast/brand combination used, if the PAR and PPFD aren't there, there's no use in using it.
So, if this guy told you that he has 2x500watt 20k bulbs and a ballast running themn, and they produce growth of the right kind then great. If not, then not so great.
If all you are after is the actual colors you eyes see and what that does in terms of making fish/coral stand out based on the color spectrum then use any old bulb, flourescent, vho, halide, led...who cares.
The heighth of the lights over the surface of the water will affect light penetration and the amount of PAR and PPFD reaching the top/middle/bottom of the tank.
Run a fan and move the lights closer and those parameters increase the closer you get to the surface.
If you start with a crappy bulb/ballast combination then sometimes even sticking the light in the water(don't try this) won't generate enough PAR/PPFD.
All situations are different even if they sound the same. No two tanks are exactly the same even if they house the same inhabitants in the same type of set-up.
Research some more on what folks have used on their systems that are similar to yours in shape/size/and stock. Look at their results and adjust them to suit your needs.
Any fan being run over the surface of the water or directed at the lights themselves, no matter size/shape/etc will help cool things down, as will the distance above the water.