Okay I'll do my best on this I'm a little pressed for time. Hopefully someone will come a long and grab what I missed.
As for the cages are you trying to figure out what manufactuer to go with? I have the Reptilebasics 2x4 for my boa's. These work great and will hold just about any size boa up to 8ft or so. If your looking for the 6ft one then there are some other great cages, but I don't have experience with them. Theres Boaphile, Animal Plastics, and PVC cages just to name a few. I have heard great things about all three.
I'll share what I know with reptilebasics. They come with optional heat, which can be 21" flexwatt, RHP 40w or 80w, and ultra-therm heat pads. Any of these will work great. It depends on the conditions you have, but from what I can see the RHP 40w or the flex-watt would be fine. For the boa's I would probably say the RHP, and for the
bp I would go with belly heat probably the flex-watt. I have both and they work great either way.
The RHP's go inside the cage at the top. They work great because they mimic the heat from the sun, and if your snake is in it's hide the hide will warm up ultimately warming up the inside as well. For larger snakes the RHP's work great also. The snake is big enough that it can absorb the heat coming down, and then it dispurses the heat back off. This actually helps raise the ambient temp's and control the ambient temps as well.
If the flex-watt is what you go with the it is built-in to the cage and the bottom has a slot for your probe! They have an optional light for an extra $20 that is enclosed in the cage and it's flueracant(don't know how to spell that lol) so it doesn't get hot at all.
I'm not sure what t-stat your thinking of, but I prefer the helix. It is the easiest most accurate t-stat I've found for around $100. Extremely easy to use.
For humidity and temps you can purchase an accurite thermometer at wal-mart or home depot for about $15. They measure temps and humidity.
I hope all got all the answers, but if I missed something just ask and I'll try to help the best I can.
