jesse summed it up - the advantage of T5's lies in the reflectors/bulbs/ballast/fans-cooling and that unit is a "bottom line" unit as far as T5's go (not that it is a bad unit -it is really nice, and would certainly consider it myself if i were setting up a 75, it will work well for you - but to keep the price down they don't go full out on all the top of the line components) - however your "pro" hasn't been watching the threads on T5's on RC and is just plain wrong!
if everything else ie FLOW, WATER QUALITY/STABILITY/CLARITY, PROPER PLACEMENT, HEALTHY SPECIMENS, ACCLIMATION TIME TO THE LIGHTS, LACK OF PREDATORS/DISEASE and everything else that matters much more then your choice of lights is good to go - then that light set will support almost any commonly kept coral including SPS and clams in a standard 75g tank all the way to the bottom, and BTW it will make a beauty of a set up asthetically with the independent controling of the actinic bulbs.
your biggest problem is going to be acclimating your exsisting corals and any future corals to that light and proper placement of some of your low light corals down low or in the sand - your shrooms will need shading protection at first from that light. remember what i said in the first post i made and add to that any new specimens will need to sit in the sandbed for a couple weeks and slowly raised to their final resting place. you can always buy better bulbs in the future too
