The news of big aquarium manufacturers such as ecotech and D&D, utilising the new Cree LED lighting technology is making me listen. Metal halide performance is becoming achievable with led lighting with many advatages, such as reduced heat, lower running costs, and much more it has to be the way to go.
The Ecotech Radion XR30 has 24 cree XP lights totaling 130 watts. these consist of blue, white and green bulbs. the unit is upgradable and its customisable functionalitly allows users to exchange firmware online. Like most things Ecotech is utilisers the 'w' wire less technology to sync with pumps to create variouse weather conditions. More information is available at ecotechmarine .
D&Ds equivalant the A1 SOL has 24 cree LED's, 16 white and 8 blue totalling 75 watts claiming high enough output to keep many SPS Corals. I beleive this unit to be aimed at the nano style aquariums like the ecotech, but this does'nt mean multiple units cant be used togeather. Variouse hanging kits are also available, again more info available at theaquariumsolution.