If it is a used fixture I would recommend replacing the bulbs, PC
's spectrum rating really only hold for around 6 months, 8 months being around the max before they are feeding the algae more then your coral.
Remember that the watts per gallon really is just a rough estimate of what you can do. It's an awesome start though.
Only thing when you are protein skimmer shopping, a lot of the bigger chains and even some shifty LFS
's will try and push you towards the coralife skimmer line. Save your money and buy an octopus or something that is a real brand, they are the biggest hunks of junk.