Constrictors NW Cages are on my list. I have several that I've been looking at, but so far, those are high on my list.

Here's my list that I've compiled.
ConstrictorsNW
Vision
Precision Cages
Showcase Cages
PVC Cages
Boaphile Plastic

I like the Showcase cages because they're really pretty to look at, but they're really expensive (but I have about 3 years to save up for it, so we'll see). But I'm not sure if they're stackable, which I do need....
I'm considering a Vision cage because they're aesthetically appealing, but I'm going to need to stack different sizes, and I don't know if that'd be possible. Plus, I think I'd want to get a cage that's larger than the largest available size than the Vision cages offer.
I think Boaphile is the company with a fairly poor customer service reputation.
Other than those ones, I haven't looked too far into the other ones. But if I can find stackable cages with a 6 foot long cage on the bottom and I can put two 3 foot cages side by side on top of them, then I'd be happy! That's what I'm really looking for! (As my goal is to have my RTB, a BRB, and at least 2-4 balls - I'd likely be adding to that).