Honestly, there are WAY too many variables that go into what wattage bulb you need for heat. I've found that outside temps, indoor temps, viv placement, whether or not there's a screen lid on the tank, type of bulb etc. all play a role in which bulb I need to use at any given time. Right now I'm using a 100W regular incandescent house light for heat and my temps are perfect. A week ago though I was using a 75W tight beam to get the right temps. The outside temps here were much different last week though.
My suggestion is to invest in a variety of bulbs and wattages and then do a little experimentation. And if you use regular incandescent bulbs instead of those expensive reptile bulbs they can always be reused in your home if you find that you can't use them in the viv.
The wattages vary from one enclosure to another. The reason for this is that you have to take into consideration the temps in your home. Also if the viv has a screened top versus a solid top or even what it's constructed of.
Your best bet is to experiment with different wattages and use your thermometer, of course, to see which one works best. For either of those size enclosures, it could be anywhere from a 60w bulb to a 100w bulb.
You can use an ordinary "bright white" household bulb for this. No need to go out and purchase an expensive basking bulb.
Hope this helps
EDIT... sorry Crissy... I did not see your post :wink: