I am trying to figure out what would be best to control my room temps in my new repitle room/office. It is a small attic-bedroom(about 12'x15', ~8' ceiling with two 8/12 roof slopes cutting the room down at about 42" up the wall) that currently has a 525 watt window a/c unit keeping it cool(no thermostat on a/c unit only low, high, etc.).

I would like to also put a small heater in the room too. I could then run both the heater and a/c unit through some thermostat setup to keep the room at a constant temperature all year long (i.e. below 76 degrees (a/c off, heater on), above 78 degrees (a/c on, heater off)).

What are your thoughts on that kind of setup and what would you all recommend using to run something like that?

...or I could replace the window a/c unit and buy one with a thermostat and purchase a heater with a thermostat and let them run themselves. Would that be a better option?