I'd go with the 150 watt pendant though you're still going to have an increase in temp regardless what you do

With the 20K bulb you should still use a 50/50 bulb in conjunction or daylight for full viewing pleasure. Try a 140000K or 50000K as they can stand alone.
For more info here's a link I stumbled across when I was going to set up my saltwater tank.
http://www.coralreefecosystems.com/l...%20temperature
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