You'll love this.
I have my Alaska Channing with the 6 inch collar feeding the cold air return of the geothermal. Works like a champ. If anything, the Alaska is too much for my little house. With the factory controller, I can not set the the the Alaska over about 40% on the coldest day and typically have the low at 10% and high at 30%. Above this setting, the Alaska pumps enough heat that the Geothermal never gets a call for heat from the thermostat.
Alaska Channing => large air filter => cold air return => Geothermal
Good for the winter, good for the summer.