Check out constrictors northwest... Many people rave about their proline cages. I am looking into getting a cserpents cage this year for my boa and many people have good things to say about his racks as well.
I could be wrong, but I don't think 2x2' would be big enough for a BP (adult female)... You could divide the 6' cage into 2 sections to accomodate adult BPs.. If they are small when you get them, dividing it into 3 sections might work temporarily, but I'd think figuring out where to put the hot spots would be an issue with it divided that much.
Animal plastics makes good looking PVC cages and they are pretty cheap, you might be able to purchase three of the smaller ones (4x2x1') for your BPs.
I have my first BP now and will probably end up doing a small rack system to accommodate her and any future BPs... She doesn't seem to come out much at all, so being able to view her like I do my boa isn't as important.