I think you've made a GREAT CHOICE on where to get your cages. I've been checking them out and that's where I'm going to get my next cages from. The 4X2 cage should be fine for one boa. Since males "normally" don't get that large it should be enough for the rest of his life. As for the female you might want to get the 6X2 cage. Females can and will grow a bit larger than males "normally". For the first few years a 4X2 cage will work for each of them. Just make sure they each have their own cage. BTW having an extra cage is a good idea in the long run.
As far as prices on "Hets". Well, the price of actual Albinos is coming down. You might want to consider getting one Albino and 1 het. I've seen Albinos as low as $635 shipped. I've seen Hets as low as $115 to 135 each. The reason I'd get one of them as an Albino is because you never know that what you got was a 100% het until it proves out. If you breed 2 hets you might get lucky and get more than 25% of the babies to be Albino. Of course, I've heard of people breeding 100% hets and getting all normal looking babies. If you have an Albino and a Het to breed you'll get "up to" 50% or more of the litter being Albino. The rest of the litter will be 100% hets. That's a whole lot better than getting "up to" 25% or more Albinos and 66% possible hets for the normal looking in a het to het breeding. 
If you choose to get hets you'll pay between $350 and $500 for a pair. If you get a Het and an Albino you'll pay between $800 and $1000 for the pair.