Oil filled radiators are best since they have settings for power. Most are now digital with built in thermostat.
I use this one in winter months set at 75 and keeps room at 79. Ceiling fan circulates hot air back down to lower level of racks.
http://www.homedepot.com/h_d1/N-5yc1...atalogId=10053
Keep in mind space heaters that blow hot air can and will act up if theirs not a steady flow of cooler air. I had one stop working when room would get in the 80s and start working once back in 70s.
Oil Radiators for the win