question is, do you currently need a skimmer?
You have a fish only tank.
How are your nitrates and phosphates?
How often are you changing water?
If they are good and your not and your happy with how often you are changing water for waste export and water maintenance, than you probably don't need a skimmer.
I might go with cycling some live rock to add to the tank to increase biofiltration before adding a skimmer unless your adding SPS or LPS to the tank and you need low nitrates and phosphates. Upgrade your HOB filter to something that will give you more flow for saltwater. IF you need to add a skimmer, there are HOBs that are better than having that all in one filter.