6x39w T5 should be enough to grow anything in that tank, assuming you get a quality reflector (individual reflectors are best)... Clams and SPS included. The heat is pretty manageable on halides as well -- a small fan or 2 is all you usually need, if anything.. Your current lighting should be sufficient for some lower light softies to start with -- some mushrooms and zoas should do fine, xenia as well..

Personally, i'd stick with Koralias until you move to a wavemaker.. A Vortech MP20/MP40 or a Tunze wavebox is uncomparable to the old switching 'wave' devices.. With the Koralias as well, you don't have to deal with the ugly old grey box in the tank... They're MUCH more aesthetically pleasing than a good old powerhead..

-Justin