The first thing to remember is every set up and situation is different. No answer is going to fit your problem exactly. My room is often 68-65ºF I use custom enclosures mostly but have 2 tanks. the issue of a tank is the open top. I would make a suggestion that will aid in heating and humidity. Side turn the tank.

http://ball-pythons.net/forums/showt...arium-Solution

It isn't a huge amount of work but is some. I have a 2 foot fluorescent light mounted inside the tank (on its side) this adds 9-12º to the ambient air temps. Over night I run a deep blue LED it runs warm enough to hold 76-77º in my enclosure. Add some insulation to the sides and back and bottom and this will help some too. I however run a second UTH run off a second t-stat I use the herpstats personally I believe the herpstat intro offers the same features as the 300 plus a few extras for a fair bit less cash. I can't say you will need a second but it is possible.