Great post and I agree with everything. But, actually I'll add a BCC from Peru has some of the most forgiving husbandry of the Boas. It's equal to the Colombian boa and the slow grown Peruvian boas can get HUGE. Rio Bravo Reptiles has some very nice Peruvian boas. They can be considered the largest of the BCC generally speaking.
There is also the Argentine boa (BCO). There is a woman on Youtube (snake hugs and kisses) I think is her name with two 11 foot, 104 pound Argentine boas. They can tolerate lower temps and humidity.
All of that said, there needs to be a plan for care. Are you able to always have a 2nd and maybe 3rd person around during cleaning and handling times? I fully appreciate large snakes, but I also know I have no business keeping one. I have a Royal python and a beautiful Colombian boa that may hit the 7 foot mark. That is as big as I feel my experience level allows. I don't have a helper, and am not prepared to go larger than a big boa.
An 8 foot BCI, BCC, or BCO is a lot of snake. For their length, they are as strong a constrictor as they come. Once those bigger pythons hit their full size though, you should not handle them alone.
The Papuan Olive and the Aussie Olive pythons do get very thick and can handle huge prey. I believe they are very expensive and not readily available in the states. Some feedback says they are a bit defensive and do not hesitate to bite.
Thinking purely from a common sense standpoint, I'd go the route of the large boas. They will challenge you, and they do have terrestrial and arboreal qualities so they are not always on the ground waiting for a meal.
Whoever mentioned a big coastal carpet python had a good idea too.
Best of luck but I'd say work up to it. Also in 6 years you may not have the same enthusiasm as you do now. Home ownership, and life sometimes requires several sacrifices. If you had a nice boa with a 6 foot cage, chances are it would not interrupt your life like a giant python would.
Good luck.
Look at these boas. http://www.mccarthyboas.com/BigSnake.html