I have a 1500 watt oil filled radiator hooked up to a Ranco. The radiator has three heat settings: Low (600w) Med (900w) or these two combined on High (1500w). The Ranco is rated to 1500w, but the surge protector it came wired with pops whenever the thermostat is on high. So, I use it on Medium. I don't know if this is a problem with the radiator surging when set on high, or if it's the surge protector.

In any case, your 6 x 7 room will not require much to warm it (provided you're not living in Siberia). Any oil filled radiator should work, but you may consider getting one with different power settings.

Jon