hmm.. for HOB for that large.. It's going to be tough, in my opinion. Your 'best bang for the buck' on a tank that size is probably a Tunze skimmer. They're not hang on, but they sit in the tank. (They don't take up that much room, IMO).. If you have extra cash, you can look into a Deltec Skimmer.
How do you feel about overflow boxes, and tying that to a sump?
That will give you a lot more options.