Spot lights or halogen bulb advice?

[Sierra1167]

I have been having trouble getting the temps up with my household bulbs since winter has hit NE Ohio. My fixtures only go up to 75 or 100 watts safely. Even 100 watt bulb just isn't cutting it.(temps are barely getting to 80-90 tops and not consistently. I have been thinking of getting spot lights because others here seem to be happy with them. I just have a few questions for those who have used them. Do the spots fit into a regular dome fixture? What size should I get for each tank? Right now I have a 20L,40gallon critter tank, a 3ftx1ftx1ft viv, and a 4ftx12x12 viv. Where have you found the best prices? Any suggestions would be apppreciated!