I would agree that 175W is adequate for a tank with those dimensions, and anticipated inhabitants. I myself run a 175W 10000K Aqualine bulb in a pendant above a 36"X18" tank. With the pendant there is no problem covering the 36" length. I am happy with it, but I do not have any real high light demanding corals. One does not necessarily get bored with softies. There are actually folks out there who prefer softies and LPS over hard corals. Having said that I believe you have enough information to guide you.
