Hydor Theo, cannot recommend them enough! I've got two, and will probably order a third this fall. I've got one of the Fluval M series, and once going it is quite reliable.
Hydor Theo 25W, will keep my 2.5 at a steady 81 degrees, he's happy as a clam.
I would be cautious about listing top fin, I've heard of a few people getting "bad" ones that cause chemical burns.