good skimmers don't come cheap, that's for sure, but you want one that is rated for at least 200 gallons IMO. Though many might disagree, but for your size system, an ASM or turbofloater might suit you well (the former being superior in design, but the latter being a little easier on the wallet) I run my 120 FOWLR with a turbofloater 1000, and as long as I keep up on the maintenance, that thing cranks out the skimmate. I'll let others chime in with their opinions regarding other brands I have no experience with.
I can say that I have a Remora skimmer for a smaller tank which I hung on the sump and it is unbelieveably efficient. They make a Remora-pro model which you might be able to hang on your sump if you can find the space. It is compact in design, and so-long as you don't have a heavily stocked tank, it might suit you well.