Another cage option is Pro-Line from Constrictors NW.
I have 3 of them and all in different sizes.
The plastic used is the best out there IMO. HDPE plastic.
Your boa will more than likely display some abroad tendencies. The Central American types usually have a knack for climbing.
If you want to ventrally set up a nice display cage, get at least 18" of ceiling.
Boaphile caging is decent, and aesthetically nice looking on the outside. The 421D (common model) is only 11" tall. The 422D is 17" and a lot more expensive.
AP has nice cages. I'd probably have one if I was not so happy with my Prolines.