2 different animals.
A power vent is an exhaust fan that mounts on the outside of the house sucking the fumes outside.
A direct vent mounts at the exit of the stove and pushes the air to the outside through some sort of insulated pipe.
Both units require electricity to operate. In addition, they require a fume switch so that in the event the heater gets clogged, it will automatically shut off the power to the stove.
If it is already hooked up to a chimney in the kitchen, it may be better to try to move that air around the house. One possible way is to get the fans that mount into the corner of the door jamb.
If you could provide some sort of description of the layout of the house it may help get some better suggestions.
Is there a basement under the house ?? Some have suggested to hook up a duct from the opposite end of the house, run it through the basement, and connect it to the blower motor intake housing to create a distribution air loop.
ETA, Dave types faster then I do.....