Upgrading lighting fixture in 38 gal reef

Hi I currently am running a 36" nova extreme t5 fixture that has two lights which gives off 39 watts each or 78 together. Ive kept soft corals and mushrooms under this fixture since I bought it with no issues but im considering getting into other types of corals that require stronger lighting. Do you guys think i need to buy a whole new fixture or should I just get another light with a similar output as my current one and keep them both on their together. Together this would be around 158 watts of lighting on a 38 gallon tank which is a little more thank 4 watts per gallon. Im not to knowledgable about lighting so if anyone has any suggestions I would really appreciate it. Thanks!!!