This Vornado Space Heater is life-changing for keeping temp regulated. It’s got a thermostat so you can set an exact temperature and it’s really good at circulating air with low noise. You might need a couple of these for 700 square feet, but it’s so nice having having “set it and forget it” even heating.

They’ve got other models too if you prefer a different look or want a remote, but I and a couple friends/family members have been using this one for years and been really happy with it.