I have a Howe radiator and went for the Spal fan with 3300cfm quiet blades largest they make..I haven't had a problem with heating up or overheating since I put it on last August. I have a thermister that turns on at 180 degrees and off at 170. It takes awhile for it to turn on in the mornings and you have to really listen to hear it.
Your in SF and shouldn't have a problem with overheating even with a electric fan..unless your really boosting alot. Most people on TT are unsuccessful with the electric fans. My vote is still out waiting on this summer.