Since you're wanting to have an SPS dominant tank, I would go with the biggest skimmer that will fit and that your budget allows.

You can't go wrong with a Reef Octopus, great "bang for your buck". I've been using a RO nw150 on my 40g (SPS dominant) for close to a year and LOVE IT!!! I bought it used (3 weeks old) for less than $100.