If you are going the HOB route, I'd recommend a Bubble Magus NAC5E skimmer
They are pretty much the closest thing to an in-sump style skimmer you can get but with the features that make them useable for display tanks without sumps. The skimmer boasts a 5" diamater body, needlewheel driven pump and will pull in 450L of air per hour. Not bad for a skimmer under the $200 mark