I ended up going with a 100w Top Fin, which is, thus far, doing a beautiful job. It took me a lot longer than I'd anticipated to get the tank set up, so I'm now just shy of 2 weeks into cycling, and with the heater set on high my tank is maintaining a respectable 85 degrees in the midst of one of the coldest winters we've had for a while (mind you, this is California, so it doesn't tend to dip much below 57 degrees in the house). Once I'm closer to adding fish I intend to purchase a second 100w & keep them both dialed much lower.
Over-all the cycle is progressing nicely. The Ph is a bit on the alkaline side (7.8 as of two days ago), but I'm getting it all evened out.
Thanks to everyone for your help.
"Don't tell fish stories where the people know you; but particularly, don't tell them where they know the fish." -Samuel Clemens