I have the same question myself, unfortunately, I'm still researching the answer. I have a 70 gallon set up for close to 2 years, and my skimmer (Red Sea Prizm) went south due to a leak where the motor housing meets the plastic body of the skimmer. As far as HOB skimmers go, I have good and bad things to say about the Prizm. First, it's loud, and kinda big, but other than that, I thought it did a pretty good job AND I love the extra media basket that you can slide in. Perfect for a little extra carbon to polish up the tank.
That said, I am looking for a change. From what I read, either an Aqua C Remora or a Reef Octopus are the two best, depending on who you ask. Comperable models are comperable in price too. I'm leaning towards the remora because I know more people that have them than don't, and the Octopus looks a little bulky, and I can't seem to find what is considered to be a good skimmer that does not have the pump inside the tank!