Hey Man,
Why are you so quick to get your mind of burms?
If you want a burm...keep one. If you know that YOU are ready then go for it.
http://www.mccarthyboas.com/BigSnake.html
Check those boa's out even though there are some obese ones, that can give you a good idea of how big they can potentially get. If you get a male Burm...honestly a big boa could be just as much work IMO. I'm talking males.
Whatever you choose to get...start of with a juvenile or hatchling.
This way you aren't overwhelmed....lets say if you got a 8-10 footer.
This way you can also grow with the snake.
Good luck!!
Mike